UNIVERSITY  OF 


AGRICULTUPJ 


WON  CIRCULATING 

CHECK  FOR  UNBOUND 
CIRCULATING  COPY 


OF 

UHWERSITY  OF 


UNIVERSITY  OF  ILLINOIS 


Agricultural  Experiment  Station 


BULLETIN  NO.  151 


BY  STEPHEN  A.  FORBES 
STATE  ENTOMOLOGIST 


URBANA,  ILLINOIS,  OCTOBER,  1911" 


CONTENTS  OF  BULLETIN  NO.  151 

PAGE. 

The   Catalpa   Sphinx    (Ceratomia  catalpa  Bdv.) 464 

The  Fall  Web-worm   (Hyphantria  textor  Harr.) 466 

The  Yellow  Poplar-Caterpillar     (Apatela  populi  Riley) 468 

The  Walnut  Caterpillar  (Datana  integerrima  G.  &  R.) 470 

The  White-marked  Tussock-moth  (Hemerocampa  leucostigma  S.  &A.)  472 

The   Brown-tail   and   Gypsy  Moths     (Euproctis    chrysorrhcea  L.,   and 

Porthetria   dispar   L. ) 476 

The  Forest  Tent  Caterpillar  (Malacosoma  disstria  Hbn.) 483 

The  Common  Canker-worm  (Paleacrita  vernata  Peck) 485 

The  Lilac  Borer  (Podosesia  syringa  Harr.) 489 

Two  Poplar  Borers  (Memythrus  tricinctus  Harr.  and  M.  dollii  Neum.)  493 

A  Viburnum  Borer  (Sesia  pictipes  G.  &  R.) 496 

The  Maple  Borer  (Sesia  acerni  Clem.) 497 

The  Ninebark  Borer  (Sesia  scitula  Harr.) 499 

The  Bag- worm  (Thyridopteryx  ephemera -formis  Harr.) 500 

The  Poplar  and  Willow  Borer  (Cryptorhynchus  lapathi  Linn.) 502 

The  Dogwood  Twig-girdler   (Oberea  tripunctata  Swederus) 506 

The  Locust  Borer   (Cyllene  robinia  Forst.) 510 

The  Oak  Twig-pruner   (Elaphidion  villosum  Fabr.) 512 

The  Bronze  Birch-borer  (Agrilus  anxius  Gory) 515 

The  Scurfy  Scale   (Chionaspis  furfur  a  Fitch) 517 

The  Oyster-shell  Scale   (Lepidosaphes  ulmi  Linn.) 519 

The  San  Jose  Scale   (Aspidiotus  perniciosus  Comst.) 520 

Putnam's  Scale   (Aspidiotus  ancyhts  Putnam) 523 

The  Walnut  or  Willow  Scale  (Aspidiotus  juglans-regia  Comst.) 523 

The  Cottony  Maple  Scale  (Pulvinaria  vitis  Linn.) 524 


SOME  IMPORTANT  INSECTS  OF  ILLINOIS 
SHADE  TREES  AND  SHRUBS 

BY  STEPHEN  A.  FORBES,  STATE  ENTOMOLOGIST 

The  protection  of  the  shade  trees  and  ornamental  shrubs  of 
Illinois  against  insects  has  been  for  several  years  a  problem  of  rap- 
idly increasing  importance.  Many  of  our  most  desirable  trees 
and  shrubs  are  liable  to  slow  destruction  by  obscure  insect 
pests  understood  little  if  at  all  by  those  immediately  con- 
cerned. Trees  which  have  grown  for  years,  becoming  more  at- 
tractive, more  valuable,  and  more  highly  valued  year  by  year,  begin 
to  weaken  and  decay,  the  owner  does  not  know  why.  This  is  often 
due  to  borers  or  to  scale  insects,  the  presence  of  which  has  not  been 
detected  or  suspected,  but  whose  injuries  might  have  been  prevented 
if  the  facts  had  been  known  in  time.  More  sudden  losses  are  fre- 
quently caused  by  overwhelming  attacks  of  leaf-eating  insects 
which,  altho  conspicuous,  are  not  dealt  with  because  proper  measures 
of  procedure  are  not  known.  Observations  and  experiments  upon 
this  subject  have  been  for  several  years  a  prominent  part  of  the  work 
of  the  office.  Beginning  in  1898,  repeated  careful  examinations 
have  been  made  of  the  trees  and  shrubs  of  the  parks  and  boule- 
vards of  Chicago,  and  this  work  has  been  extended  from  time  to 
time  to  other  cities  and  towns  thruout  the  state.  With  the  estab- 
lishment of  a  field  assistant  in  Chicago  in  1907,  the  subject  received 
more  continuous  attention  at  the  hands,  first,  of  Mr.  H.  E.  Hodg- 
kiss  and,  later,  of  Mr.  John  J.  Davis,  the  latter  of  whom  espe- 
cially has  made  many  studies  of  the  life  histories  of  species  previ- 
ously but  little  known,  and  has  added  a  mass  of  details  to  our 
knowledge  of  the  subject  in  all  its  parts. 

The  general  subject  is  still  under  investigation,  and  will  be  in 
due  time  reported  upon  in  a  much  fuller  and  more  elaborate  article, 
but  the  present  brief  preliminary  paper  has  been  prepared  in  the 
hope  that  it  may  be  found  of  immediate  practical  use  to  municipal 
authorities  in  control  of  parks,  boulevards,  and  streets,  to  town  im- 
provement societies,  and  to  owners  of  lawns  and  other  private 
premises  the  appearance  of  which  they  are  striving  to  improve  by 
the  use  of  trees  and  shrubs. 


464  BULLETIN  No.  151  ^  [October, 

THE  CATALPA  SPHINX 
(Ceratomia  catalpce  Bdv.) 

One  of  the  most  destructive  of  the  few  insects  to  which  the 
catalpa  tree  is  subject  is  a  large  showy  caterpillar  known  as  the 
catalpa  sphinx  (Fig.  i).  It  is  a  southern  insect,  and  has  not  been 
found  in  this  state  north  of  Clay  and  Richland  counties,  altho  it  has 


F  g.  l.  Catalpa  Sphinx  (Ceratomia  catalpa?.):  a,  egg  mass;  b,  newly  hatched 
larvae;  c.  d,  larvae  one-third  grown  and  one  joint  showing  its  dorsal  pattern; 
«t  /,  ff,  h,  i,  mature  larvae,  variously  marked,  and  single  joints  showing  dorsal 
patterns;  j,  pupa;  k,  moth;  I,  egg,  enlarged;  others  all  slightly  less  than 
natural  size.  (Ohio  Experiment  Station.) 


191 1]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE  TREES   AND    SHRUBS  465 

extended  up  the  Atlantic  coast  as  far  as  New  Jersey.  It  is  likely 
to  appear  suddenly  in  large  numbers  upon  single  trees,  stripping 
them  completely. 

The  full-grown  caterpillar  (Fig.  i,  e,  f,  h)  is  rather  strongly 
marked,  with  a  broad  velvety  black  stripe  on  the  back  and  sulphur- 
yellow  sides  spotted  with  black,  while  the  under  side  of  the  body  is 
pale  green.  It  is  unusually  variable  in  color,  however,  there  being 
both  light  and  dark  forms.  It  is  from  two  and  a  fourth  to  three 
inches  long,  and  has  a  hornlike  appendage  projecting  from  the 
hinder  end  of  the  back.  The  young  caterpillars  (Fig.  I,  c)  are 
pale  yellow  and  spotted  with  black.  There  are  probably  but  two 
generations  in  Illinois.  The  caterpillars  leave  the  trees  and  go 
into  the  ground  to  pupate  (Fig.  2). 


Fig.  2.    Catalpa  Sphinx,  Ceratomia 
catalpce,  pupa  in  cell  in  earth. 

The  parent  insect  is  a  large  heavy-bodied  moth  (Fig.  i,  fc)  with 
strong,  narrow,  brownish-gray  wings,  with  obscure  lines  and  spots 
of  black.  The  eggs  (Fig.  i,  a)  are  laid  in  masses  on  the  leaves, 
sometimes  as  many  as  a  thousand  in  a  bunch,  and  the  young,  on 
hatching,  feed  at  first  in  companies — a  fact  which  makes  it  easy  to 
destroy  them  if  their  presence  is  detected  early,  by  picking  off  or 
spraying  the  infested  leaves.  A  general  spraying  of  a  tree  with 
arsenate  of  lead  or  Paris  green  will  destroy  the  caterpillars  at  any 
time.  Professor  H.  Carman,  of  Kentucky,  says  that  the  nearly 
grown  worms  can  be  shaken  or  jarred  down  from  most  catalpa 
trees  and  readily  destroyed  by  hand. 


466 


BULLETIN  No.  151 
THE  FALL,  WEB-WORM 


[October, 


(Hyphantria  textor  Harris) 

The  fall  web-worm  is  the  only  common  Illinois  insect  which 
makes  a  large  conspicuous  web  in  late  summer  and  in  fall,  inclos- 
ing a  considerable  number  of  the  leaves  and  twigs  of  a  branch,  together 


Fig.  3.    Pall  Web-worms,  Hyphantria  textor,  and  their  web,  on  apple-tree. 
(New  Hampshire  Experiment  Station.) 


/9//1       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS 


467 


with  a  colony  of  caterpillars  which  feed  under  its  protection  (Fig. 
3).  It  is  un fortunately  often  called  in  Illinois  the  tent  caterpillar, 
but  the  latter  name  is  properly  applied  only  to  a  caterpillar,  not 
often  seen  in  this  state,  which  makes  a  small  compact  web  in  the 
forks  of  a  branch  in  spring,  which  it  uses  only  for  protection  while 
not  eating. 

The  web-worm  is  an  almost  universal  feeder  and  has  been 
found  on  about  a  hundred  and  twenty  species  of  fruit,  shade,  and 
ornamental  trees,  upon  the  leaves  of  which  it  feeds.  It  is  one  of 
the  most  annoying  pests  of  the  tree  grower,  its  numerous  large 
webs,  enclosing  brown,  skeletonized  leaves,  making  the  tree  very 
unsightly,  and  the  injury  done,  as  it  spreads  from  branch  to  branch, 
often  being  considerable.  While  the  caterpillars  are  growing  they 
do  not  wander  from  their  common  web,  but  enlarge  this  to  cover 
fresh  leaves  as  fast  as  those  within  it  are  devoured.  When  they 
have  nearly  completed  their  growth,  however,  they  scatter  far  and 
wide,  running  briskly  about  when  disturbed,  and  feeding  on  almost 


Fig.  4.  Fall  Web-worm.  Hyphantria  textor:  a,  b, 
larvas,  light  and  dark  varieties;  c,  pupa;  d,  moth, 
spotted  variety.  All  slightly  enlarged.  (New  Hamp- 
shire Experiment  Station.) 


468  BULLETIN  No.  151  [October, 

every  green  thing  they  find.  At  this  time  they  become,  when  very 
abundant,  an  extremely  destructive  and  annoying  pest. 

They  are  about  an  inch  long  when  full  grown,  varying  from  pale 
yellow  or  grayish  to  a  dark  bluish-black  hue.  (Fig.  4,  a,  &.)  The 
body  is  covered  with  long  straight  hairs  grouped  in  tufts  rising 
from  small  black  or  orange-yellow  tubercles,  of  which  there  are  a 
number  on  each  segment.  When  mature,  the  caterpillars  go  to  the 
ground,  into  which  they  burrow  a  short  distance,  or  they  creep 
under  shelter  above  ground,  where  they  form  slight  cocoons  of 
silken  web  interwoven  with  the  hairs  from  their  bodies.  Within 
these  they  change  to  dark  brown  pupae  (Fig.  4,  c),  and  in  this  con- 
dition they  pass  the  winter.  The  moths  emerge  in  spring  and 
lay  their  eggs  in  broad  patches  of  several  hundred  each,  on 
the  under  side  of  the  leaves  near  the  end  of  a  branch,  late  in 
May  and  early  in  June.  The  adult  insect  is  usually  pure  white, 
but  is  sometimes  white  spotted  with  black.  There  are  either  one 
or  two  broods  of  this  species,  according  to  the  latitude,  two  in 
southern  and  central  Illinois  and  probably  but  one  in  the  northern 
part  of  the  state. 

The  simplest  and  most  effective  method  of  controlling  these 
insects  is  to  destroy  their  webs,  and  the  caterpillars  within  them, 
either  by  cutting  off  the  twigs  which  bear  them  and  crushing  or 
burning  them  immediately,  or  by  burning  the  webs  on  the  tree. 
A  bundle  of  rags  or  a  few  corn-cobs,  or  even  a  porous  brick,  wired 
to  the  end  of  a  pole  long  enough  to  reach  the  nest  and  saturated 
with  kerosene,  makes  a  good  torch  for  the  purpose.  Care  must 
be  taken,  however,  not  to  injure  the  tree,  and  to  destroy  the  scat- 
tering worms  which  may  drop  from  the  nest  without  being  killed. 
Where  the  infestation  is  too  general  to  make  this  method  con- 
venient, or  where  the  webs  are  so  high  in  the  trees  that  they  can 
not  be  readily  reached,  a  spray  of  arsenate  of  lead  will  eventually 
kill  the  web-worms  as  they  extend  their  webs  over  the  poisoned 
foliage.  Paris  green  may  be  used  instead,  but  the  lead  arsenate 
is  to  be  preferred  because,  being  much  more  adhesive,  it  lasts  longer 
on  the  tree.  This  method  is  most  effective  when  the  caterpillars 
are  young,  since  they  are  then  extending  their  webs  rapidly  and  are 
likely  to  be  more  promptly  poisoned  than  when  they  are  virtually 
full  grown. 

THE  YELLOW  POPLAR- CATERPILLAR 
(Apatela  populi  Riley) 

The  prominence  of  the  Carolina  poplar  as  a  city  tree,  especially 
in  situations  where  it  is  difficult  to  find  any  other  which  can  en- 
dure the  conditions  prevailing,  makes  it  the  duty  of  the  Entomolo- 
gist to  discuss  the  insect  enemies  of  even  this  rather  inferior  va- 
riety. 


IMPORTANT   INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  469 

Among  those  which  have  recently  been  found  most  injurious 
to*  the  poplar  is  a  large  and  rather  handsome,  light  yellow  or  pale 
green,  very  hairy  caterpillar  (Fig.  5),  most  easily  known  by  five 
long  pencil-like  tufts  of  black  hairs  rising  one  behind  the  other  on 
the  middle  line  of  the  back,  the  first  on  the  fourth  segment  of  the 
body  and  the  fifth  on  the  last.  This  caterpillar  was  particularly  in- 
jurious to  poplars  and  considerably  so  to  willows  in  Chicago  in 
1909.  It  has  been  noticed  by  us  also  in  Peoria,  Danville,  and  East 
St.  Louis.  It  feeds  on  the  leaves  in  midsummer  and  again  in  fall, 
there  being  two  generations  in  a  year.  It  sometimes  completely 


Fig.  5.    The  Yellow  Poplar-Caterpillar,  Apatela  popuii, 
natural  size. 

strips  a  tree,  rendering  it  unsightly  and  putting  it  in  poor  condition 
to  withstand  unfavorable  conditions  or  to  resist  the  attacks  of 
more  destructive  insects. 

The  caterpillar  when  full  grown  is  about  an  inch  and  a  half  long, 
the  skin  yellowish-green,  and  the  long,  soft,  drooping  hairs  yellow. 
The  pencil-like  tufts  referred  to  rise  from  the  fourth,  sixth,  sev- 
enth, and  eleventh  segments,  those  on  the  seventh  and  eighth  being 
the  smallest.  The  head  is  shining  black  and  there  are  black  spots 
on  the  top  of  segments  one  and  two.  The  young  are  almost  white, 
and  the  black  tufts  of  hairs  are  shorter,  but  still  conspicuous.  The 
caterpillar  is  of  a  sluggish  habit,  and  when  at  rest  it  commonly  lies 
curled  up,  with  the  ends  of  the  body  together.  When  full  grown 
it  spins  a  loose,  pale  yellow  cocoon  of  silk  interwoven  with  its 
own  hairs.  This  is  generally  placed  in  a  crevice  of  the  bark,  under 
the  edge  of  a  fence  board,  or  in  some  similar  sheltered  place.  The 
winter  is  passed  in  this  chrysalis  stage,  from  which  a  large,  pale 
gray  moth  emerges  the  following-  May. 

The  caterpillars  are  most  easily  destroyed  when  young,  for  they 
do  not  at  first  scatter  from  the  branch  upon  which  they  were  born. 


470  BULLETIN   No.   151  [October, 

Later  they  can  readily  be  collected  singly  by  hand  from  trees  of 
small  size,  or  they  may  be  poisoned,  like  most  of  the  leaf  feeders, 
by  spraying  with  arsenicals  when  they  are  active  on  the  tree. 

THE  WALNUT  CATERPILLAR 
(D  at  ana  integerrima  G.  &  R.) 

The  most  annoying  insect  enemy  of  the  walnut  is  a  blackish, 
somewhat  striped,  hairy  caterpillar  (Fig.  6),  an  inch  and  a  half 
long  when  full  grown,  which  eats  the  leaves  during  the  latter  part 
of  the  summer,  often  largely  denuding  the  tree.  It  makes  itself 
particularly  offensive  on  lawns  by  dropping  quantities  of  refuse 
from  the  tree  and  by  crawling  over  walks  and  buildings  when  it 
comes  down  to  go  into  the  ground. 

This  caterpillar  is  readily  distinguished  by  its  loose  coat  of 
soft  whitish  hairs,  and  particularly  by  its  habit  of  raising  both  ends 
of  the  body  when  at  rest  and  throwing  itself  into  this  position  and 
jerking  sidewise  when  disturbed.  It  often  attracts  attention  by  col- 
lecting in  masses  upon  the  larger  branches  or  the  trunk  of  the  tree 
preliminary  to  molting,  piling  up  in  this  way  two  or  three  layers 
deep.  When  full  grown  it  comes  down  the  trunk  to  the  ground, 
wanders  about  to  a  short  distance  and  enters  the  earth  an  inch  or 
two,  changing  there  to  a  reddish-brown  or  blackish-brown  chrysalis 
(Fig.  6,  B).  In  this  stage  it  winters,  emerging  the  following  sum- 
mer, mainly  in  June  and  July,  in  the  form  of  a  buff-brown  moth 
(Fig.  6,  A)  with  darker  bands  across  the  fore  wings.  The  females 
lay  their  eggs  in  clusters  varying  from  seventy-five  to  a  hundred, 
according  to  some  observers,  and  from  five  hundred  to  twelve 
hundred,  according  to  others,  and  the  young  hatching  from  these 
feed  in  dense  clusters,  completely  devouring  every  leaf  as  they  go. 
When  all  the  leaves  on  one  twig  or  branch  are  destroyed,  they  mi- 
grate to  another,  sometimes  in  a  distant  part  of  the  tree.  They 
lose  their  gregarious  habit  as  they  mature,  and  by  the  time  they  are 
full  grown  they  scatter  here  and  there  over  the  greater  part  of 
the  tree.  There  is  but  a  single  generation  in  a  year. 

Altho  they  are  most  frequently  seen  on  the  walnut,  they  are 
common  on  butternuts  and  hickories,  and  are  a  pest  to  the  grower 
of  the  pecan.  They  have  likewise  been  found  on  beech,  oak,  willow, 
honey-locust,  apple,  and  thorn.  Trees  in  the  forest  are  not  likely 
to  suffer,  but  those  on  streets  and  lawns  are  sometimes  so  completely 
stripped  by  September  that  they  stand  almost  as  naked  as  in  mid- 
winter, only  the  green  nuts  remaining  on  the  branches. 

This  account  of  their  habits  is  sufficient  to  suggest  various  avail- 
able methods  of  destroying  them.  On  trees  small  enough  to  be 
reached  they  can  be  readily  killed  while  young  by  clipping  off  the 


797 1]       IMPORTANT   INSECTS  OF   ILLINOIS   SHADE  TREES   AND   SHRUBS 


471 


infested  twigs  on  which  the  caterpillars  are  grouped  in  colonies. 
They  are  particularly  exposed  to  attack  as  they  assemble  in  masses 
for  their  later  molts,  when  a  light  spray  of  kerosene  will  readily 
kill  them.  They  are  also  susceptible  to  arsenical  poisons  sprayed 


F/g.  6.    Walnut  Caterpillar,  Datana  integerrima:    A,  moth;  B,  pupae.    Natural  size. 
(Kentucky  Experiment  Station.) 


472      ,  BULLETIN  No.   151  [October, 

upon  the  leaves,  but  these  must  be  used  in  unusual  strength.  We 
have  found  three  pounds  of  arsenate  of  lead  to  fifty  gallons  of  wa- 
ter sufficient  to  kill  the  full-grown  caterpillars.  On  one  occasion 
a  tree  nearly  fifty  feet  high  was  effectively  sprayed  by  the  aid  of  a 
twenty-eight-foot  ladder  and  a  twelve-foot  extension  rod  with  a 
nozzle  on  the  end,  about  twenty- five  gallons  of  the  spray  being  nec- 
essary for  a  thoro  treatment.  If  these  various  measures  have 
been  neglected  and  the  caterpillars  have  left  the  tree,  they  may  still 
be  disposed  of  in  the  pupa  stage  by  digging  up  and  working  over 
the  ground  under  the  branches  and  for  a  little  distance  outside,  to 
a  depth  of  three  or  four  inches. 

THE  WHITE-MARKED  TUSSOCK-MOTH 
(Hemerocampa  leucostigma  S.  &  A.) 

The  most  destructive  leaf -eater  infesting  shade  trees  in  the 
larger  cities  of  Illinois  and  especially  in  Chicago  is  the  caterpillar  of 
the  white-marked  tussock-moth.  It  often  completely  defoliates  large 
trees,  those  most  seriously  injured  being  the  elm,  the  soft  maple, 
the  linden,  the  birch,  and  the  horse-chestnut.  (Fig.  7.)  Almost 
every  kind  of  tree,  excepting  conifers,  is  subject  to  its  attack,  and 
it  sometimes  becomes  decidedly  injurious  in  orchards.  In  Chi- 
cago it  has  been  noted  as  injurious  to  apple,  box-elder,  hard  maple, 
Norway  maple,  poplar,  willow,  oak,  ash,  locust,  hickory,  catalpa, 
and  sycamore,  and  to  several  shrubs,  including  dogwood,  button- 
bush,  Viburnum,  and  bladdernut  (Ptelea).  In  September  and 
October,  1910,  it  was  found  in  every  one  of  eighteen  towns  visited 
by  Mr.  John  J.  Davis,  present  in  small  numbers  in  seven  of  them, 
common  in  nine,  and  in  destructive  numbers  in  two. 

This  is  a  well-marked  insect,  very  easily  recognized,  especially 
the  caterpillar  and  the  egg  mass — the  two  conditions  against  which 
measures  of  destruction  must  be  taken.  The  hairy  caterpillar  (Fig. 
8),  bright  yellow  in  general  color  and  striped  with  black,  and  about 
an  inch  and  a  half  long  when  full  grown,  is  a  really  beautiful  object. 
It  may  be  known  by  its  coral-red  head,  by  two  plumelike  tufts  of 
long  black  hairs  projecting  upward  and  forward  from  the  back  near 
the  head,  by  a  single  similar  tuft  at  the  hind  end  of  the  body,  and 
especially  by  four  thick,  short,  brushlike  clusters  of  cream-colored 
hairs  arranged,  one  behind  the  other,  in  front  of  the  center  of  the 
back.  In  this  condition  it  may  be  found  upon  infested  trees  in 
June,  July,  and  August. 

There  are  two  generations  of  the  caterpillar  in  a  year  in  north- 
ern Illinois,  possibly  three  farther  south.  The  egg  masses  (Fig.  9) 
from  which  the  caterpillars  hatch  may  be  found  in  fall,  winter,  and 
early  spring.  They  form,  when  first  deposited,  frothy,  oval,  snowy 


/9//]       IMPORTANT   INSECTS  OF  ILLINOIS   SHADE  TREES   AND   SHRUBS          473 


Fig.  7.  Linden  tree  in  a  park  in  Chicago,  defoliated  by  larvae 
of  White-marked  Tussock-moth  (Hemerocampa  leucostigma).  The 
few  leaves  on  the  tree  have  all  appeared  since  the  defoliation. 

white  patches  about  an  inch  in  length,  on  the  tree  trunks,  in  the 
crotches  of  the  larger  branches,  or  in  other  more  or  less  sheltered 
places,  such  as  the  edges  of  weather-boards  and  the  under  sides  of 
the  eaves  of  porches.  Conspicuous  objects  at  first,  their  color,  under 
exposure  to  the  sooty  air  of  Illinois  towns,  is  soon  deadened  to  a 
dirty  gray.  The  caterpillar  begins  to  hatch  from  the  over-wintering 
egg  masses  about  the  middle  of  June  in  Chicago  (June  18  in  1909) 
and  gets  its  growth  in  about  a  month.  Feeding  at  first  on  the  under 
side  of  the  leaf,  which  it  skeletonizes  by  eating  off  the  soft  tissue, 
it  later  eats  inward  from  the  edge  of  the  leaf,  devouring  everything 
except  the  principal  veins. 


474 


BULLETIN  No.   151 


[October, 


The  young  caterpillars  drop  down,  hanging  by  silken  threads, 
when  the  tree  is  jarred,  and  sometimes  spin  down  without  being  dis- 
turbed, when  they  may  be  blown  to  a  considerable  distance  by  the 


Fig.  8.    White-marked  Tussock-moth,  Hemerocampa 
leucostigma,  larva.    Natural  size. 

wind.  When  nearly  full  grown,  they  are  great  travelers,  going 
from  tree  to  tree  and  even  moving  in  large  numbers  from  a  de- 
foliated tree  to  others  near  by.  When  full  grown,  the  caterpillar 


Fig.  9. 


White-marked  Tussock-moth,  Hemerocampa  leucostigma,  cocoons 
and  egg  masses  on  tree  trunk  in  a  park  in  Chicago. 


i9i i]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  475 


spins,  on  the  tree,  a  delicate  grayish  cocoon  of  silken  web  mixed  with 
its  own  long  hairs.  It  changes  to  a  pupa  within  a  few  hours  after 
the  cocoon  is  finished  and  continues  in  this  condition  from  ten  days 
to  two  weeks. 

The  adults  are  moths,  the  females  (Fig.  10)  of  which  differ 
very  widely  from  the  males  (Fig.  n)  in  the  fact  that  they  are 
almost  absolutely  wingless.  The  males  have  good  wings  and  at 


Pig.  11.  White-marked 
Tussock-moth,    Hemero- 
campa  leucostigma,  male. 
Natural  size. 
Fig.  10.    White-marked  Tussock- 
moth,     Hemerocampa     leucostigma, 
female  and  egg  masses.     Natural 
size.      (Connecticut     Experiment 
Station.) 

least  the  average  power  of  flight.  They  are  of  an  ashy  gray  color, 
with  dark  wavy  bands  across  the  fore  wings,  a  small  black 
spot  on  the  outer  edge  near  the  tip,  a  blackish  stripe  be- 
yond this,  and  a  minute  white  crescent  near  the  hind  angle. 
The  wings,  when  expanded,  measure  about  one  and  a  fourth 
inches  across.  The  female  has  little  of  the  appearance  of  a 
moth,  her  wings  being  reduced  to  the  merest  rudiments.  Her 
thick,  oblong-oval  body  is  of  a  light  gray  color,  with  rather 
long  legs,  and  is  distended  with  eggs.  When  she  comes  out 
she  lays  her  egg  mass  on  the  cocoon  from  which  she  emerged — a  fact 
which  makes  it  plain  that  the  species  can  spread  only  by  way  of  the 
wandering  caterpillars,  or  by  the  transportation  of  egg  masses  on 
young  trees.  The  eggs  of  the  last  generation  are  ordinarily  pro- 
duced in  September  and  the  winter  is  passed  in  this  condition. 

Many  insect  parasites  infest  the  pupa  and  do  much  towards  hold- 
ing the  species  in  check.  They  are  not  usually  abundant  enough, 
however,  to  control  it  completely.  In  the  fall  of  1907,  for  example, 
one  of  my  assistants  reported  that  75  percent  of  the  cocoons  of 
the  tussock-moth  in  the  Chicago  parks  were  parasitized,  but  the 
caterpillars  were  nevertheless  very  numerous  and  destructive  the 


476  BULLETIN  No.   151  [October, 

following  year.  Birds  eat  them,  but  not  freely  enough  in  the  larger 
cities  to  reduce  their  numbers  materially. 

Three  measures  of  destruction  are  applicable  to  this  pest  and 
sufficient  for  its  control.  These  are  the  destruction  of  the  egg 
masses  in  winter,  banding  trunks  of  uninfested  trees  in  spring,  and 
spraying  infested  trees  in  summer.  The  trunks  and  larger  branches 
of  trees,  as  well  as  all  objects  surrounding  those  infested  the  season 
before,  should  be  carefully  examined  in  winter  and  spring  for  egg 
masses,  and  all  these  within  reach  should  be  scraped  or  cut  away 
and  burned  or  otherwise  destroyed.  Those  beyond  convenient  reach 
may  be  killed  in  place  by  touching  each  egg  mass  with  a  sponge  or 
brush  attached  to  the  end  of  a  long  pole  and  dipped  in  crude  creosote. 

As  the  insect  spreads  from  tree  to  tree  only  in  the  caterpillar 
stage,  an  uninfested  tree  may  usually  be  protected  completely  by 
banding  the  trunk  in  such  a  way  that  the  caterpillars  from  adjacent 
trees  can  not  climb  beyond  the  band.  Sometimes,  however,  the 
branches  of  trees  intermingle  or  touch  in  such  a  way  that  the  cater- 
pillars may  go  from  one  tree  to  the  other  without  coming  down 
to  the  ground.  These  bands  should  be  applied  to  the  tree  soon 
after  the  caterpillars  begin  to  appear  in  spring,  and  they  should 
be  renewed  from  time  to  time  as  they  are  made  useless  by  exposure 
to  the  weather. 

Either  one  of  two  kinds  of  bands  may  be  used.  The  trunk 
may  be  surrounded,  at  a  convenient  height,  by  a  belt  nine  inches 
wide  of  what  is  known  as  tree  tanglefoot,  applied  with  a  brush; 
or  bands  of  cotton  batting  about  four  inches  wide  may  be  tied 
closely  about  the  tree  by  a  string  passed  around  the  middle  of  the 
band,  the  upper  half  of  which  should  then  be  turned  down  over  it. 

Where  the  preceding  measures  have  been  neglected  and  trees 
are  being  defoliated,  the  injury  may  be  stopped  by  spraying  with 
Paris  green  or  arsenate  of  lead.  This,  however,  is  a  difficult  and 
somewhat  expensive  operation  with  large  trees,  and  may  be  ren- 
dered unnecessary  by  destroying  the  egg  masses  and  banding  the 
trees  as  above  described. 

THE  BROWN-TAIL  AND  GYPSY  MOTHS 
(Euproctis  chrysorrhcea  Linn,  and  Porthetria  dispar  Linn.) 

These  two  frightful  insect  pests,  altho  present  in  America, 
the  first  for  about  forty  years  and  the  second  for  nearly  half  as 
long,  have  neither  of  them  become  established  in  Illinois,  or  indeed 
made  any  permanent  appearance  outside  of  New  England.  It  will 
probably  be  long  before  the  gypsy  moth  becomes  an  inhabitant  of 
this  state,  its  powers  of  migration  being  limited  to  the  larva.  The 
female,  altho  well  provided  with  wings,  has  a  very  heavy  body, 
and  does  not  fly.  The  brown-tail  moth,  on  the  other  hand,  is  a 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE  TREES   AND    SHRUBS 


477 


strong,  swift  flier,  and  is  virtually  certain  to  occupy  the  whole 
country  in  due  time,  and  it  is  further  particularly  likely  to  be  in- 
troduced into  the  state  direct  from  its  European  habitat  on  nursery 
stock  imported  from  France.  It  winters  in  the  caterpillar  stage 
partly  grown,  hundreds  of  young  collecting  in  single  colonies  on  the 
trees,  where  they  hibernate  in  closely  webbed  nests  (Fig.  12).  Hun- 
dreds of  these  nests  containing  living  young  were  sent,  in  1909,  in- 


Fig.  12.     Brown-tail  Moth,  Euproctis  chrysorrfuza,  winter  nests.    Natural 
size.    (Connecticut  Experiment  Station.) 

to  Illinois  from  France,  and  only  the  most  active  and  fortunate  in- 
spection work  prevented  their  escape  in  this  state  that  winter.  Worse 
than  this,  however,  infested  cases  of  nursery  stock  originating  in 
France  were  reshipped  into  Illinois  from  other  states  where  the 
force  of  inspectors  was  not  sufficient  to  deal  with  the  shipments 
arriving,  and  danger  from  these  sources  will  continue  year  after 
year  unless  other  states  strengthen  their  inspection  systems.  Fur- 
thermore, since  stock  received  in  Iowa  was  shipped  to  this  state 
that  winter  bearing  living  brown-tail  caterpillars,  it  is  extremely 
likely  that  the  part  retained  in  Iowa  was  similarly  infested  and 
that  the  brown-tail  has  thus  obtained  a  lodgment  there  and  possibly 
in  other  states  adjacent  to  Illinois.  If  this  is  the  case  it  will  pres- 
ently spread  to  our  state  also,  especially  as  -the  moth  flies  long  dis- 
tances before  the  prevailing  winds.  It  is  important,  for  these  rea- 


478 


BULLETIN  No.  151 


[October, 


sons,  that  our  people  should  be  fully  informed  and  carefully  in- 
structed in  advance  in  order  that  the  first  of  these  insects  to  appear 
may  be  detected  and  destroyed  without  delay. 

The  brown-tail  moth  is  a  caterpillar  (Fig.  13)  in  the  destruc- 
tive stage,  and,  of  course,  goes  thru  the  four  stages  of  egg,  larva, 
pupa,  and  adult.  It  is  easily  distinguished  in  the  last  of  these  stages 


Fig.  14.  Brown-tail  Moth,  Eu- 
proctis  chrysorrhcea.  Slightly  en- 
larged. (Massachusetts  Experi- 
ment Station.) 


Fig.  13.  Brown- tail 
Moth,  Euproctis  chrys- 
orrficsa,  larva.  Natural 
size.  (Massachusetts 
Experiment  Station.) 

from  any  American  insect  by  the  character  to  which  it  owes  its 
name  of  "brown-tail,"  namely,  a  thick  brushlike  tuft  of  orange- 
brown  hairs  at  the  tip  of  the  abdomen,  especially  in  the  female 
(Fig.  14).  Otherwise  both  sexes  are  pure  white  thruout,  except 
that  occasionally  there  may  be  a  few  black  spots  on  the  fore  wing  of 
the  male.  They  measure  about  an  inch  and  a  quarter  from  tip  to 
tip  of  the  expanded  wings.  Any  pure  white  moth  of  approximate- 
ly this  size  with  an  orange-brown  tuft  of  hairs  at  the  tip  of.  the 
abdomen  may  be  at  once  set  down  as  the  brown-tail;  and  any  one 
seeing  it  in  Illinois  will  render  a  notable  public  service  by  reporting 
the  fact  promptly  to  the  State  Entomologist,  at  Urbana,  111. 

The  winter  nests  of  these  caterpillars  are  also  easily  identi- 
fied, since  no  native  Illinois  species  hibernates  on  either  tree  or 
shrub  in  colonies  of  living  caterpillars  inclosed  in  a  web.  Any 
such  cluster  of  young  caterpillars  so  protected  by  a  common  web 
may  consequently  be  set  down  at  once  as  the  brown-tail  and  should, 
of  course,  be  promptly  destroyed  and  the  facts  reported  to  the 
Entomologist.  Nurserymen  importing  European  seedling  stock  can 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  479 

not  guard  too  carefully  against  the  accidental  importation  of  this 
insect  pest,  as  it  is  widespread  in  Europe,  breeding  abundantly  on 
hedges,  trees,  and  various  shrubs,  and  making  its  way  into  the 
nursery  from  infested  surroundings. 

The  brown-tail  feeds  upon  practically  all  deciduous  trees  and 
many  shrubs  and  even  upon  herbs.  Thousands  of  fruit  trees  in 
the  vicinity  of  Boston  have  been  killed  by  it,  and  damage  to  maples 
and  elms  in  wooded  regions  has  caused  the  forest  to  appear  brown 
in  June,  an  injury  which,  if  repeated  for  three  or  four  years,  has 
killed  many  trees.  As  the  caterpillars  pass  the  winter  about  a  quar- 
ter grown,  they  begin  to  devour  the  leaves  of  trees  as  soon  as  these 
put  out  in  spring,  and  even  eat  the  buds  and  blossoms  before  the 
leaves  have  spread.  Old  trees  may  thus  lose  all  their  buds,  or,  if 
not,  the  foliage  itself  may  be  devoured  at  a  later  date. 

The  caterpillar  reaches  its  full  size  in  New  England  during  the 
last  half  of  June,  and  the  moths  emerging,  fly  about  and  lay  their 
eggs  some  twenty  days  later.  The  small  round  eggs  are  laid  in 
brownish  masses  (Fig.  15)  on  the  under  side  of  leaves,  each  mass 


Fig.  15.  Brown-tail  moth,  Euproctis  chrys- 
orrfCxa,  egg  masses  on  leaves.  Natural  size. 
(Connecticut  Experiment  Station.) 

two-thirds  of  an  inch  long  by  a  fourth  of  an  inch  wide,  and  con- 
taining about  three  hundred  eggs.  The  full-grown  caterpillar  is 
about  two  inches  long,  reddish-brown,  with  an  interrupted 
white  stripe  on  each  side  and  two  red  dots  on  the  back  near 
the  hind  end.  It  is  also  blotched  with  orange  and  is  cov- 
ered with  tubercles  bearing  long  barbed  hairs,  those  on  the 
back  and  sides  with  short  brown  hairs  additional,  which  give 
them,  when  magnified,  a  velvetlike  look.  The  young  hiber- 
nating larvae  are  blackish,  with  reddish-black  hairs  and  black 
heads.  The  pupa  is  formed  among  the  leaves  on  the  infested  tree 
or  shrub,  most  frequently  at  the  tips  of  the  branches,  where  sev- 
eral caterpillars  may  spin  a  loose  web  together,  each  forming,  how- 


480  BUTXETIN  No.  151  [October, 

ever,  its  own  cocoon  within  the  web.  When  the  insect  becomes 
abundant,  cocoons  may  be  found  under  fences  and  at  the  edge 
of  clapboards  on  houses,  and  in  many  similar  places. 

One  of  the  most  disturbing  peculiarities  of  a  brown-tail  in- 
festation is  the  fact  that  the  long  barbed  hairs  already  mentioned 
are  covered  with  a  poisonous  excretion,  and  that  they  readily  pierce 
the  skin,  causing  an  irritating  rash  which  occasionally  results  in 
serious  illness.  "Indeed,"  says  Dr.  Howard,  "it  is  not  necessary 
for  the  caterpillar  itself  to  come  in  contact  with  the  skin;  at  cer- 
tain times  of  the  year  it  seems  as  though  the  hairs  were  actually 
floating  about  in  the  air.  At  the  time  of  the  caterpillar's  change 
of  skin,  and  particularly  at  the  time  of  the  spinning  of  the  cocoon 
and  the  final  change,  certain  of  these  hairs  appear  to  become  loos- 
ened in  such  a  way  that  they  are  carried  by  the  wind."  Others 
report  that  these  poisoned  hairs  may  collect  on  clothing  hanging  on 
the  line,  to  the  intense  annoyance  of  those  who  wear  it. 

The  readiest  and  most  obvious  means  of  controlling  the  brown- 
tail  moth,  and  certainly  the  easiest  one,  is  the  collection  and  destruc- 
tion of  the  winter  nests  after  the  leaves  have  fallen.  After  April 
the  only  practical  remedy  is  spraying  the  trees  with  an  arsenical 
mixture.  The  young  caterpillars  are  readily  enough  destroyed  with 
arsenate  of  lead,  but  the  older  ones  become  resistant  to  poison 
sprays,  and  as  much  as  five  pounds  of  the  arsenate  to  a  barrel  of 
water  has  been  found  necessary  to  kill  the  full-grown  caterpillar. 

When  this  insect  appears  within  our  borders  it  will  be  most 
destructive  in  parks  and  towns  and  forest  plantations,  since  these 
are  not  regularly  sprayed  and  will  require  a  special  treatment  to 
protect  them.  It  will  also  aid  the  San  Jose  scale  in  putting  out 
of  business  the  neglectful  or  indifferent  orchardist,  but  the  business 
fruit  grower,  who  values  his  property  and  takes  care  of  it  as  well 
as  he  can,  will  have  much  less  to  fear  from  this  insect,  since  his 
ordinary  spraying  operations  will  be  practically  certain  to  destroy 
it  as  it  enters  his  orchard.  The  fact,  however,  that  the  full-grown 
caterpillar  requires  a  heavier  insecticide  treatment  than  does  the 
codling-moth  and  the  canker-worm,  for  which  most  of  our  spray- 
ing is  done,  may  make  it  necessary  to  go  over  the  orchard  in  winter 
to  remove  and  destroy  the  hibernating  colonies. 

The  gypsy  moth  may  be  more  briefly  considered,  altho  it 
is  even  a  more  destructive  pest  than  the  brown-tail,  especially  for 
the  reason  that  it  eats  the  leaves  of  evergreens — trees  which  are 
often  killed  by  a  single  defoliation.  It  is  conveyed  to  distances  in 
the  caterpillar  stage  only  by  accident.  Passing  wagons,  automo- 
biles, trolley  cars,  or  even  railroad  trains,  may  carry  the  cater- 
pillars to  uninfested  districts,  but  in  this  way  its  spread  is  slow, 
especially  as  all  possible  measures  are  being  taken  in  infested  dis- 
tricts of  New  England  to  keep  the  roadsides  free  from  the  pest, 


IMPORTANT   INSECTS  OF  ILLINOIS   SHADE  TREES   AND   SHRUBS  481 

and  thus  to  reduce  to  a  minimum  the  possibility  of  an  extensive 
spread. 

The  caterpillar  of  the  gypsy  moth  (Fig.  16)  is  a  voracious  feed- 
er, eating  the  leaves  of  nearly  every  kind  of  tree  or  shrub,  and  de- 
vouring sometimes  also  grasses  and  field  and  garden  crops.  The 
very  fact  that  it  spreads  but  slowly  makes  it  locally  all  the  more 


Fig.  16.   Gypsy  Moth,  Porthetria  dupar,  larvae.    Natural  size. 
(Connecticut  Experiment  Station.) 

injurious,  since  it  accumulates  in  enormous  numbers  upon  infested 
localities.  Forests,  orchards,  gardens,  parks,  and  street  shrubs  and 
trees  may  be  stripped  of  every  leaf  between  the  first  of  May  and 
the  middle  of  July. 

The  insect  winters  in  the  egg  stage,  the  eggs  being  plastered 
in  conspicuous  masses  (Fig.  17)  on  the  trunks  of  trees  and  on  va- 
rious other  objects.  They  may  readily  be  destroyed  by  touching 
them  with  a  mixture  of  creosote  oil,  50  percent,  carbolic  acid,  20 
percent,  turpentine,  20  percent,  and  coal-tar,  10  percent,  in  sufficient 
quantity  to  soak  the  mass.  The  caterpillar  may  also  be  killed  on  the 
trees  with  arsenical  poisons,  but  these  must  be  applied  in  unusual 
quantities,  since  the  gypsy  moth  is  not  readily  poisoned  in  the  cater- 
pillar stage.  Five  pounds  of  arsenate  of  lead  to  fifty  gallons  of 
water  will  kill  the  young,  but  even  this  can  not  be  depended  upon 
for  the  full-grown  caterpillars.  These  are  about  three  inches  long, 
of  a  sooty  or  dark  gray  color.  Along  the  back  is  a  double  row 


482  BULLETIN  No.   151  [October, 

of  blue  spots,  followed  by  a  double  row  of  red  spots,  and  the  back 
is  marked  with  yellow.  The  cocoon  is  formed  among  the  leaves 
like  that  of  the  brown-tail  and  the  moths  appear  from  the  middle 
of  July  to  the  middle  of  August.  The  male  is  bluish-yellow,  ex- 
panding about  an  inch  and  a  half,  and  the  female  (Fig.  17)  is 


Pig.  17.    Gypsy  Moth,  Porthetria  dispar;  female  moths,  laying  eggs  on  bark.     Natural  size. 
(Connecticut  Experiment  Station.) 

nearly  white,  somewhat  spotted  and  barred  with  black.  Its  wing 
expanse  is  about  two  and  a  fourth  inches.  The  female  is  very  slug- 
gish and  so  heavy  that  she  can  not  fly;  but  the  male  is  an  active 
flier. 

The  oval  egg  masses,  about  one  and  a  half  inches  long  by 
three-fourths  that  in  width,  are  laid  in  summer  on  the  trunks  of 
trees,  on  fences,  on  the  sides  of  houses,  and  in  various  other  places 
Large  holes  in  old  trees  are  often  found  filled  with  them.  The 
caterpillars  feed  principally  at  night,  especially  after  they  reach 
some  size,  and  they  seek  to  hide  during  the  day,  often  coming  down 
upon  the  larger  limbs  and  trunk  of  the  infested  tree  in  search  of 
hiding  places.  This  habit  has  led  to  the  use  of  bands  of  burlap 
tied  around  the  trunks  of  trees,  under  which  the  caterpillars  may 
rest  during  the  day  and  where  they  can  be  easily  destroyed  by  hand. 

The  probabilities  of  widespread  destruction  to  forest,  park,  and 
orchard  properties  by  these  insects  are  greatly  reduced  by  the  truly 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS 


483 


tremendous  and  unexampled  work  being  done  by  the  United  States 
Department  of  Agriculture  and  the  state  of  Massachusetts  in  bring- 
ing from  Europe  the  native  parasites  of  these  insects.  This  work 
is  making  successful  progress,  and  it  is  all  the  more  hopeful  because 
the  parasites  of  both  these  species  seem  to  keep  them  substantially 
in  check  in  the  Old  World,  where  they  rarely  become  seriously 
destructive. 

THE  FOREST  TENT  CATERPILLAR 
(Malacosoma  disstria  Hbn.) 

There  occasionally  appears  in  the  forest  region  of  southern 
Illinois  an  overwhelming  eruption  of  caterpillars  which  denude 
large  areas  of  woodlands,  especially  the  oaks  and  the  maples,  and 
the  black  and  sweet  gum  trees,  and  thence  invade  orchards,  parks, 
and  town  premises,  carrying  the  same  destruction  to  fruit  and  shade 
trees  generally.  This  is  one  of  the  species  which  moves  in  masses 
such  as  actually  to  delay  the  passage  of  railroad  trains,  piling  up 


Fig.  18.     Baltimore  Oriole  attacking  nest  of  Forest  Tent  Cater- 
pillar, Malacosoma  disstria.     (New  Hampshire  Experiment  Station.) 


484 


BULLETIN  No.  151 


[October, 


on  the  rails  several  inches  deep.  It  is  known  to  entomologists  as 
the  forest  tent  caterpillar,  but  in  the  South  it  is  commonly  called 
"the  caterpillar"  simply.  The  name  of  "tent  caterpillar"  is,  in  fact, 
inappropriate  for  it,  since  it  spins  but  little  and  never  makes  a  tent. 
It  is  closely  allied,  however,  to  the  common  tent-caterpillar  of 
eastern  orchards  and  has  received  its  common  name  because  of  this 
resemblance. 

When  full  grown  (Fig.  19)  it  is  about  two  inches  long  and  a 
quarter  of  an  inch  thick.  It  is  of  a  brownish  general  color,  and  is 
conspicuously  marked  with  a  series  of  whitish  or  cream-colored 
spots  down  the  middle  of  the  back.  On  the  upper  part  of  each  side 


Fig.  19.    Forest  Tent  Caterpillar,  Malacosoma 
disstria,  larva.    Natural  size. 

is  a  Bather  broad  blue  line  edged  above  and  below  with  a 
yellowish-brown  line.  When  disturbed  it  drops  from  the  branch 
and  hangs  suspended  in  mid-air  by  means  of  a  fine  thread 
spun  from  the  mouth.  In  moving  about  on  the  tree  these  cater- 
pillars follow  each  other  in  single  file.  They  feed  mostly  in  the 
tops  of  the  trees,  often  eating  out  the  central  part  of  the  base  of  a 
leaf,  allowing  the  remainder  to  fall  to  the  ground.  When  preparing 
to  molt,  they  mass  together  on  the  limbs  and  may  continue  thus  for 
a  day  or  two.  They  often  form  similar  masses  in  stormy  weather 
and  in  general  when  at  rest.  The  eggs  (Fig.  20)  are  laid  in  a 
thick  hard  band  around  a  twig  and  covered  with  an  impervious 
varnish.  From  these  the  young  hatch  in  early  spring,  sometimes 
before  the  appearance  of  the  leaves  on  which  they  depend  for  food. 


Fip.  20.  Forest  Tent  Caterpillar, 
Malacosoma  disstria:  e,  egg  ring  re- 
cently laid;  g,  hatched  egg  ring. 
Slightly  enlarged.  (Cornell  Ex- 
periment Station.) 


Fig.  21.  Forest  Tent  Cater- 
pillar, Malacosoma  disstria: 
m,  male;  /,  female.  Natural 
size.  (Cornell  Experiment 
Station.) 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  485 

They  are  capable,  however,  of  fasting  for  a  considerable  time  with- 
out injury,  and  they  may  even  survive  the  destruction  of  the  leaves 
by  late  frosts.  They  scatter  for  pupation  late  in  May  or  early  in 
June,  spinning  cocoons  which  they  fasten  among  clusters  of 
leaves  or  exposed  on  fences  and  in  other  similar  situations.  There 
is  but  a  single  generation  in  a  year.  The  parent  moths  (Fig. 
21 )  measure  about  an  inch  and  a  quarter  across  the  expanded 
wings.  The  general  color  is  brownish-yellow  and  the  fore  wings 
are  marked  by  two  straight  dark  brown  lines  which  cross  them 
obliquely,  parallel  with  each  other  and  the  hinder  edge. 

Trees  may  be  protected  by  spraying  with  arsenical  poisons 
shortly  after  the  young  caterpillars  begin  to  appear,  or  by  clipping 
off  in  winter  the  twigs  bearing  the  conspicuous  belts  of  eggs  and  de- 
stroying these  by  burning.  Even  overwhelming  hordes  may  be  ar- 
rested by  surrounding  the  tree  trunk  with  a  band  of  cotton  batting 
about  four  inches  wide,  tied  around  the  middle  with  a  string,  the 
upper  part  being  then  turned  downward  over  the  string.  Or,  the 
trunk  may  be  surrounded  with  a  band  of  printers'  ink  applied  as 
described  in  the  article  concerning  the  common  canker-worm 
(P-  488). 

THE  .COMMON  CANKER-WORM,,  OR  SPRING  CANKER-WORM 
(Paleacrita  vernata  Peck) 

The  common  canker-worm  is  best  known  as  a  pest  of  the  apple 
orchard,  but  it  is  sometimes  even  more  destructive  to  elms  (Fig.  22) 
than  to  apple-trees.  It  feeds  also  on  cherry,  at  first  eating  small 
holes  thru  the  leaves,  but  when  larger  devouring  the  whole  leaf  ex- 
cept the  midrib  and  some  of  the  coarser  veins.  Modern  methods 
of  orchard  management  require  a  regular  and  frequent  spraying 
with  arsenical  poisons  as  a  protection  of  fruit  against  the  codling- 
moth,  and  this  has  the  incidental  effect — often  unnoticed  by  the 
orchardist — of  speedily  killing  off  any  colony  of  canker-worms 
which  may  have  chanced  to  make  a  start  in  the  orchard.  Hence 
it  is  only  neglected  orchards,  or  those  not  in  bearing  either  because 
too  young  or  by  reason  of  a  crop  failure  for  the  year,  which  are 
liable  to  serious  canker-worm  injury. 

With  the  elm,  however,  the  case  is  different.  The  canker-worm 
lives  on  this  tree  as  willingly  and  successfully  as  on  the  apple.  Elms 
are  rarely  sprayed  in  Illinois,  and  if  the  canker-worm  once  comes 
to  infest  them  there  is  no  natural  end  to  the  injury  except  the  death 
of  the  tree,  unless,  indeed,  the  parasites  of  the  insect  and  other 
natural  checks  on  its  increase  may  happily  suppress  it  before  that 
event. 


486 


BULLETIN  No.   151 


[October, 


The  spraying  of  large  elms  is,  of  course,  a  difficult  and  expen- 
sive operation,  and  canker-worms  are  less  susceptible  to  arsenical 
poisons  than  many  other  insects.  There  is,  however,  a  much  cheaper 
and  more  convenient  method  of  protecting  the  elm,  by  which  ad- 
vantage is  taken  of  two  features  in  the  economy  of  the  insect. 
When  the  caterpillars  are  full  grown  they  leave  the  tree  to  pupate 
in  the  earth,  and  the  female  moth  emerging,  being  wholly  without 
wings,  can  only  reach  the  tree  to  lay  her  eggs  by  climbing  up  the 


1 


Fig.  28.    Injury" to  elms  at  Calamus  Lake,  Niantic,  Illinois, 
by  common  Canker-worm  (Paleacrila  vetnata). 

trunk.  If  this  is  encircled  at  the  proper  time  by  a  sticky  band  im- 
passable by  her  or  by  young  canker-worms  just  hatched  from  the 
egg,  the  tree  is  virtually  secure  against  canker-worm  injury  except 
as  worms  may  reach  it  from  neglected  trees  with  which  its  own 
branches  interlace. 

Altho  the  female  canker-worm  (Fig.  23,  b)  is  wingless,  the 
male  (Fig.  23,  a)  has  two  pairs  of  rather  large,  thin,  ashy  or 
brownish-gray  wings,  the  first  pair  with  a  broken  whitish  band  near 
the  outer  edge  and  three  interrupted  brownish  lines  between  that 
and  the  body.  There  is  also  a  short  oblique  black  mark  near  the 
tip  of  the  wing,  and  a  black  line  at  its  edge  at  the  base  of  a  fringe 
of  hairs.  The  eggs  (Fig.  24,  &)  are  about  .03  of  an  inch  long,  oval 
in  outline,  and  of  a  pearly  luster  at  first,  changing  to  yellowish- 
green  with  a  golden,  greenish,  or  purplish  iridescence.  They  are 


/9//]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND   SHRUBS 


487 


laid  in  irregular  masses,  often  as  many  as  a  hundred  together,  and 
usually  .hidden  in  crevices  of  the  bark  of  trees. 

The  female  comes  out  of  the  ground  to  lay  her  eggs  from 
February  to  April,  the  date  varying  with  the  latitude  and  the  sea- 
son. The  young  caterpillars  appear  about  the  time  that  the  apple- 
tree  unfolds  its  leaves,  commonly,  in  this  state,  in  April  or  early 
May,  and  they  usually  get  their  growth  in  about  a  month  from  the 
time  when  they  issue  from  the  eggs.  They  then  go  into  the  ground 
to  a  depth  of  two  to  five  inches,  each  one  in  a  small  cell,  where 
they  change  to  the  chrysalis,  remaining  there  until  the  following 


Fig.  23.  Common  Canker-worm,  Paleacrita 
vernata:  a,  adult  male;  6,  female;  c,  portion 
of  female  antenna;  d,  joint  of  abdomen,  en- 
larged; e,  ovipositor. 


Fig.  24.  Common  Canker- 
worm,  Paleacrita  vernata:  a, 
larva;  b,  cluster  of  eggs,  nat- 
ural size,  with  one  enlarged:  c, 
side  view  of  one  of  the  seg- 
ments, d,  back  view  of  same, 
both  enlarged. 


winter  or  early  spring,  when  the  change  to  the  adult  insect  takes 
place.  There  is  thus  but  a  single  generation  produced  each  year. 
The  canker-worm  is  widely  distributed  thruout  the  country  and 
may  occur  in  destructive  numbers  in  any  part  of  Illinois.  Its  feeble 
power  of  locomotion  prevents  its  rapid  spread  in  any  locality,  but 
by  concentration  of  its  injuries  it  is  the  more  destructive  where  it 
does  occur. 

In  its  injurious  or  caterpillar  stage  (Fig.  24,  a)  it  is  readily 
recognized.  It  has  a  long  and  slender  form  and  the  habit  of  a 
"looper"  or  measuring  worm.  When  not  eating  it  usually  adheres 
only  by  its  hinder  prolegs,  extending  the  body  from  this  point  of 
support  at  an  angle  of  about  45  degrees.  As  it  is  colored  much  like 
the  bark  of  a  tree,  it  then  has  the  appearance  of  a  stubbed  twig.  It 
also  has  the  habit  of  spinning  down  from  the  tree  at  the  end  of  a 
thread,  particularly  if  the  branch  is  jarred  or  shaken.  Both  the  just- 
mentioned  habits  are  doubtless  advantageous  to  it ;  the  first  by  con- 
cealing it  to  some  degree  from  the  observation  of  birds  and  the 
second  by  putting  it  beyond  their  reach.  The  full-grown  canker- 
worm  is  about  nine-tenths  of  an  inch  in  length  and  may  vary  from 
greenish-yellow  or  gray  to  dusky  or  even  dark  brown,  with  paler 
stripes  along  the  sides.  A  close  examination  will  show  also  two 
light  lines  running  close  together  along  the  middle  of  the  back. 


488  BULLETIN   No.   151  (October, 

The  young  are  usually  olive-green.  The  wingless  female,  with  its 
small  gray  body  from  a  quarter  to  two-fifths  of  an  inch  in  length 
and  its  rather  long  legs,  gives  more  the  impression  of  a  spider  than 
that  of  a  moth.  The  chrysalis  is  pale  grayish-brown,  with  a  dark 
green  tinge  on  the  wing  sheaths,  and  measures  about  a  third  of  an 
inch  in  length. 

This  insect  has  not  recently  been  abundant  in  Chicago,  but  its 
capacities  for  injury  are  well  illustrated  in  a  recent  attack  on  elms 
at  Big  Rock,  Kane  county.  Some  ten  years  ago  it  was  generally 
prevalent  thruout  the  south-central  part  of  the  state,  both  in 
towns  and  in  forests,  to  which  it  had  apparently  escaped  from  neg- 
lected orchards,  although  in  some  cases  orchards  were  invaded  in 
turn  from  adjacent  forests.  A  most  threatening  attack  was  made 
on  the  magnificent  old  elms  of  Jacksonville,  but  a  vigorous  cam- 
paign, first  of  spraying  and  later  of  the  application  of  adhesive 
bands,  presently  brought  the  outbreak  under  control.* 

A  cheap  and  available  band  for  the  trunk  of  a  tree  is  made  by 
laying  around  the  trunk  first  a  strip  of  unglazed  cotton  batting 
two  or  three  inches  wide  and  over  this  a  four-  to  six-inch  strip- of 
tarred  paper  tied  around  the  middle  with  ordinary  wrapping  twine. 
Upon  this  paper  belt  should  be  spread  a  layer  a  quarter  of  an  inch 
thick  of  cheap  printers'  ink  with  which  a  small  amount  of  car  wheel 
oil  has  been  mixed,  just  enough  to  make  it  easy  to  spread.  If  the 
tarred  belt  becomes  slightly  hardened  by  exposure  so  as  to  permit 
an  insect  to  cross,  it  may  be  made  sticky  again  by  brushing  it  with 
a  little  of  the  same  kind  of  oil.  The  cotton  batting  beneath  the 
paper  is  necessary  to  keep  the  young  canker-worms  or  the  female 
moths  from  crawling  up  behind  the  paper  where  the  roughness  of 
the  bark  would  give  them  passageway.  These  bands  should  be 
placed  on  the  tree  as  early  as  the  middle  of  February  or  the  first 
of  March,  the  time  varying  according  to  the  latitude,  and  they  may 
be  safely  removed  by  the  middle  of  June.  The  cost  of  the  bands 
will  approximate  ten  cents  a  tree. 

If  the  canker-worms  have  already  ascended  the  tree,  it  is  some- 
times necessary  to  spray  the  leaves  with  an  arsenical  poison,  which 
may  be  either  arsenate  of  lead  or  Paris  green,  the  latter  at  the  rate 
of  one  pound  of  the  poison  and  one  pound  of  lime  to  seventy-five 
gallons  of  water.  If  the  arsenate  of  lead  is  used,  three  pounds  of 
it  dissolved  in  fifty  gallons  of  water  will  kill  even  the  full-grown 
caterpillars. 

*The  Canker-worm  on  Shade  and  Forest  Trees.  By  S.  A.  Forbes.  Twen- 
ty-second Report  State  Ent.  111.,  page  139. 


191 1]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND   SHRUBS  489 

THE  LILAC  BORER 
(Podosesia  syringes  Harris) 

Among  the  borers  whose  instincts  lead  the  female  to  choose, 
for  the  deposit  of  her  eggs,  scars  or  injured  places  on  the  bark  of 
trees  and  shrubs,  with  the  effect  greatly  to  increase  the  injury  and 


Fig.  25.  Trunk  of  ash  in  one  of  the  parks  in  Chicago,  showing  injury 
by  the  Lilac  Borer,  Podosesia  syringce. 

to  prevent  its  healing,  is  a  species  commonly  known  as  the  lilac 
borer  (Podosesia  syringes},  because  it  was  first  noticed  to  infest 
lilacs.  It  is  much  more  important,  however,  by  reason  of  its  in- 
juries to  various  species  of  true  ashes,*  and  to  the  mountain  ash, 

*It  has  been  found  injurious  to  the  lilac  (Syringa  sp.),  to  the  mountain 
ash  (Sorbus  americana),  and  to  the  white,  green,  and  English  ashes  (Frax- 
inus  americana,  lanceolata,  and  excelsior). 


490 


BULLETIN   No.   151 


[October, 


Fig.  36.  Trunk  of  ash,  in  one  of  the  parks  in  Chicago,  showing  injury 
by  the  Lilac  Borer,  Podosesia  syringce. 

on  the  trunks  and  branches  of  which  it  produces  large,  rough,  scar- 
like  outgrowths  from  knots,  roughened  places,  or  wounds,  by  un- 
dermining the  bark  and  boring  into  the  wood.  (See  figures  25  and 
26.) 

The  eggs  are  laid  in  summer  in  masses  on  rough,  scarred,  or 
knotty  places.  They  hatch  in  about  six  days  and  the  young  borers 
eat  thru  the  bark  into  the  outer  layers  of  the  sapwood,  where 
they  mine  irregularly  about,  penetrating  the  harder  wood  and  go- 
ing to  the  center  of  small  branches.  (Fig.  27.)  In  fall,  when  they 
are  nearly  or  quite  full  grown,  they  make  a  hibernating  cell  by 
plugging  up  the  burrow  both  before  and  behind  with  frass,  and 
there  they  pass  the  winter  as  larvae.  They  do  practically  no  bur- 


1911}       IMPORTANT   INSECTS  OF  ILLINOIS   SHADE  TREES   AND   SHRUBS 


491 


rowing  in  spring,  but  pupate  in  April  or  the  first  part  of  May.  As 
a  preparation  for  pupation,  they  burrow  outward  and  cut  their 
way  thru  the  bark,  leaving  only  a  thin  outer  film  to  close  the  pupal 
cavity.  By  means  of  short  teeth  with  which  each  segment  of  the 
abdomen  is  armed,  the  pupa,  when  mature,  works  its  way  out  of 


Fig.  28.  Lilac  Borer,  Podo- 
sesia  syringce,  larva.  About 
5  times  natural  size. 

Fig.  27.  Lilac  Borer,  Pod- 
osefia  syringoR.  Burrows 
in  ash  made  by  larvae. 
Slightly  reduced. 

its  gallery  until  it  projects  some  three-quarters  of  an  inch.  The 
winged  insects,  altho  moths,  closely  resemble  wasps  in  movement, 
color,  and  form.  They  make  their  appearance  from  the  latter  part 
of  April  to  the  middle  of  June  in  central  and  northern  Illinois. 

The  borer  or  larva  (Fig.  28)  is  very  variable  in  length.  It  is 
white,  yellowish  anteriorly,  the  head  of  a  bright  mahogany  color, 
becoming  very  dark  at  the  mandibles,  which  are  stout,  broad,  and 
provided  with  five  teeth.  The  segments  of  the  body  are  distinctly 


492  BULLETIN   No.   151  [October, 

marked,  somewhat  flattened,  the  first  segment  reddish  and  leathery 
above,  the  last  with  a  broad  yellowish  patch. 

The  moth  (Fig.  29)  has  a  black  head,  a  deep  brown  thorax 
more  or  less  marked  with  bright  chestnut-red,  and  a  black  abdomen 
sometimes  marked  with  chestnut,  but  sometimes  with  a  small  yel- 
low spot  on  each  side  of  the  fourth  segment,  or  with  the  segments 
banded  with  yellow.  The  femora  are  black,  the  anterior  pair  of 
the  tibiae  orange,  the  middle  and  hind  tibiae  black  with  orange  bands. 


Fig.  29.    Lilac  Borer,  Podosesia  syringes,  adult. 
Slightly  enlarged. 

The  tarsi  are  yellow,  the  hind  pair  with  a  black  band  above.  The 
fore  wings  are  deep  brown,  with  a  violaceous  luster  and  usually 
with  a  rusty  red  dash  on  the  outer  part.  At  the  base  is  a  transpar- 
ent streak.  The  hind  wings  are  transparent  and  yellowish,  the 
veins,  discal  marks,  and  margins  deep  brown,  sometimes  tinged 
with  red. 

The  spread  of  the  wings  is  from  an  inch  to  nearly  an  inch  and 
a  half,  the  females  being  considerably  larger  than  the  males. 

This  insect  is  very  abundant  and  destructive,  especially  to  the 
green  ash  in  Chicago  parks,  and  has  been  bred  by  us  also  from  the 
white  ash  at  Kankakee.  Its  injury  is  very  noticeable  and  character- 
istic, especially  on  the  trunks  of  small  trees.  Sometimes  the  smaller 
branches  break  off  at  the  point  of  injury,  but  this  does  not  usually 
happen  until  after  the  moth  has  escaped.  George  D.  Hulst  says, 
writing  of  these  insects  in  New  York:  "In  this  section  they  are 
very  destructive  to  both  lilac  and  English  ash.  Large  shrubs  of 
lilac  are  now  very  rarely  seen,  and  the  English  ash  is  being  rapidly 
exterminated.  In  the  latter  I  have  seen  the  wood  completely  rid- 
dled with  the  holes  made  by  the  larvae  and  the  entire  tree  dead." 

To  check  the  multiplication  of  the  species  and  the  spread  of  the 
injury  it  will  be  sufficient  to  cut  away  and  burn  infested  branches 


IMPORTANT   INSECTS   OF   ILLINOIS    SHADE   TREES   AND   SHRUBS  493 

and  trees  in  winter.  It  may  also  be  practicable  to  protect  trees  espe- 
cially exposed  by  painting  rough,  knotty,  and  injured  places  on  the 
bark  with  a  poison  mixture  commonly  used  by  orchardists  to  prevent 
infestation  by  ordinary  borers.  A  number  of  substances  are  avail- 
able for  this  purpose,  the  simplest  of  which,  perhaps,  is  a  mixture 
of  soft  soap  and  soda,  with  the  addition  of  Paris  green.  The  fol- 
lowing is  a  convenient  formula :  To  a  saturated  solution  of  wash- 
ing soda  add  soft  soap  sufficient  to  make  a  thick  paint,  and  to  each 
ten  gallons  of  this  wash  add  a  pint  of  crude  carbolic  acid  and  half  a 
pound  of  Paris  green.  This  may  be  painted  thickly  upon  scarred, 
roughened,  or  knotty  surfaces  in  April  and  early  May  and  renewed 
as  necessary  until  August. 


Two  POPLAR  BORERS 

(Memythrus  tricinctus  Harris) 

(M.  dollii  Neum.) 

Two  boring  caterpillars,  similar  in  appearance,  but  differing  in 
the  larval  or  boring  stage  mainly  in  size,  infest  poplars  in  this  state 
to  an  injurious  degree.  They  are  most  destructive  to  young  nursery 
trees,  particularly  to  the  balm  of  Gilead  (Populus  candicans},  but 
the  Carolina  poplar  (P.  deltoides},  Figure  30,  is.  also  sometimes 
badly  infested.  They  are  generally  present  thruout  Chicago,  often 
infesting  trees  which  are  likewise  injured  by  a  boring  larva,  Cryp- 
torhynchus  lapathi,  discussed  on  p.  502.  They  have  also  been  found 
by  us  in  park  and  street  trees  in  several  Illinois  cities  and  towns 
from  Centralia  northward.  In  the  case  observed  by  us  in  Chicago, 
the  eggs  of  one  of  these  species,  which  one  we  do  not  know,  were 
deposited  July  22,  mostly  in  a  crevice  of  the  bark  or  in  the  neigh- 
borhood of  a  bud,  and  young  larvae  were  first  seen  July  26,  altho 
some  of  these  had  apparently  hatched  at  least  a  week  before.  The 
borers  winter  in  the  larval  stage  in  the  wood,  pupate  in  spring,  and 
come  out  as  winged  moths  in  June  and  July — at  various  dates  from 
June  18  to  July  26,  if  we  may  judge  by  results  obtained  in  our  in- 
sectary.  From  a  willow  in  Cook  county  a  specimen  of  M.  tricinctus 
was  bred  which  emerged  July  2. 

The  boring  larvae  are  whitish  caterpillars,  with  brown  or  yellow- 
ish heads  and  a  smooth  neck  shield.  The  two  species  are  most  easily 
distinguished  by  the  markings  of  the  head  and  by  the  number  of 
hooks  on  the  abdominal  legs.  In  M.  tricinctus  the  head  is  yellowish 
and  mottled  with  large  patches  of  brown,  while  the  abdominal  feet 
have  from  eighteen  to  twenty-two  hooks  in  a  row.  In  M.  dollii 


494 


BULLETIN  No.  151 


[October 


(Fig.  32)  the  head  is  brown  with  large  darker  patches  on  the  sides, 
and  a  black  band  or  blotch  between  the  antennae.  The  abdominal 
feet  have  ten  to  fifteen  hooks  in  each  row.  Both  these  species  are 


•T 


Fig.  30.    Small  poplar  infested  with  sesiid  borers  (Memythrus). 


distinguished  from  some  other  borers  of  their  family  by  the  fact 
that  the  first  segment  of  the  thorax  bears  two  oblique  dark  marks, 
approaching  each  other  behind. 


/<?//]       IMPORTANT   INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS 


496 


The  winged  insects  are  readily  distinguished  by  a  comparison  of 
the  wings  and  abdomens.  In  tricinctus  (Fig.  35)  the  fore  wings 
are  violaceous-black,  the  hind  wings  are  transparent,  and  the  ab- 
domen is  black  with  three  or  four  yellow  bands.  In  dollii  (Fig. 
36)  the  fore  wings  are  brown,  the  hind  wings  are  brown  and 


Fig.  31.  Poplar  Borer, 
Memyttirus  tricinctus  or 
dol  it,  egg.  Greatly  en- 
larged. 


Fig.  32.  Poplar  Borer,  Mem^thrus  dollii,  larva. 
About  3 t  mes  natural  size. 


opaque,  except  at  the  base,  and  the  abdomen  is  brown,  sometimes 
with  one  or  more  yellow  bands. 

In  our  work  with  these  borers  it  was  not  at  first  known  that  two 
species  were  concerned,  and  the  larvae  were  not  distinguished  in  our 
notes.  It  was  only  when  the  adults  appeared  that  the  specific  dis- 
tinctions were  established. 


Fig.33.  Poplar  Borer, 
Memyihrus  tricinctus  or 
M.  dollii,  pupa.  About 
3  times  natural  size. 


Fig.  34.  Poplar  Borer, 
Memylhrus  tricinctus  or  M. 
dollii,  anal  end  of  pupa. 
Greatly  enlarged. 


496 


BULLETIN  No.  151 


[October, 


Fig.  35.    Poplar  Borer,  Memythrus  tricinctus, 
adult  female.     About  twice  natural  size. 


A  third  species,  allied  to  the  two  above  mentioned,  but  more 
commonly  found  infesting  ninebark  (Opulaster  opulifolius),  has 
been  once  bred  by  us  from  poplar  at  Chicago. 


Fig.  36.    Poplar  Borer,  Memythrus  dollii,  adult.    About 
twice  natural  size. 


A  VIBURNUM  BORER 
(Sesia  pic  tip  es  G.  &  R.) 

A  boring  caterpillar,  somewhat  larger  than  that  described  from 
ninebark  and  dogwood,  but  otherwise  extremely  similar,  has  been 
found  doing  considerable  damage  to  viburnum  shrubs  in  all  the 
parks  of  Chicago,  and,  in  one  case,  to  wild  black  cherry  at  Riverside. 
It  burrows  beneath  the  bark,  frequently  killing  the  branches.  It 
spends  the  winter  in  the  larval  stage,  and  has  emerged  in  our  breed- 
ing cages  during  the  latter  part  of  June,  from  the  twentieth  to  the 
twenty- fourth.  Elsewhere  it  is  reported  to  emerge  during  June  and 
July.  The  species  is  known  also  from  plum,  cherry,  beach-plum, 
peach,  Juneberry,  and  chestnut,  and  has  been  bred  from  the  black- 
knot  of  the  plum. 

The  placing  of  the  eggs  has  not  been  noticed  by  us.  but  another 
observer,  Dr.  Bailey,  found  a  cluster  of  them,  ninety-two  in  number, 


/pi/]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREKS   AND    SHRUBS  497 

on  the  under  surface  of  loosened  bark  a  few  inches  from  the  root  of 
a  badly  infested  plum-tree. 

The  removal  and  destruction  of  infested  branches  at  the  proper 
time  of  the  year,  that  is,  during  the  winter  and  spring,  is  the  only 
measure  practicable  for  the  control  of  this  pest. 

The  winged  insect  has  a  blue-black  head,  thorax,  and  abdomen, 
the  thorax  with  a  narrow  pale  line  each  side,  and  the  abdomen  with 
a  narrow  pale  yellow  ring  on  the  second  and  fourth  segments,  en- 
circling the  body  completely  on  the  latter.  The  fore  wings  are 
transparent,  with  very  narrow  blue-black  margins,  and  a  narrow, 
straight,  discal  mark.  The  inner  margin  is  sometimes  scaled  with 
pale  yellow.  The  hind  wings  are  transparent,  with  a  very  narrow 
outer  margin  and  no  discal  mark.  The  spread  of  the  wings  is  from 
15 — 26  mm.,  the  smaller  specimens  being  males. 

•*£, 

THE  MAPLE  BORER 
(Sesia  acerni  Clem.) 

The  worst  of  the  borers  of  the  maples,  both  hard  and  soft,  very 
common  and  destructive  to  soft  maples  in  Chicago,  and  common 
also  in  towns  thruout  the  state,  is  a  white  or  nearly  white  caterpillar 
(Fig.  37,  a)  about  half  an  inch  long  when  full  grown,  with  a  yel- 
low head  and  a  neck  shield  of  a  paler  tint.  It  is  especially  injurious 
to  young  trees,  but  usually  originates  in  some  surface  injury  which 
attracts  the  parent  moth  in  search  of  a  place  of  deposit  for  her  eggs. 


Fig.  37.  Maple  Borer,  Sesia  acerni:  a,  a, 
larvae;  b,  b,  b,  cocoons;  c,  adult;  d,  pupal 
skin  left  in  mouth  of  burrow. 


498  BULLETIN   No.   151  [October, 

It  burrows  mainly  just  beneath  the  bark,  where  it  can  be  found  and 
destroyed  in  fall  or  early  spring.  It  comes  to  maturity  in  May  or 
June,  eats  its  way  nearly  thru  the  bark,  and  pupates  the.re.  We 
collected  the  adult  in  considerable  numbers,  at  electric  lights,  in  Ur- 
bana,  from  May  18  to  June  3,  1887.  When  ready  for  its  transfor- 
mation the  pupa  wriggles  partly  out  of  its  burrow,  and  the  adult 
insect  escaping  leaves  the  empty  pupa-case  still  sticking  in  the  open- 
ing, which  is  about  an  eighth  of  an  inch  across.  (Fig.  37,  d.~) 

The  adult  is  a  handsome  wasplike  moth  (Fig.  37,  c;  Fig.  38) 
with  thin  transparent  wings,  a  slender  yellow  body  banded  and 
trimmed  with  red,  and  a  brushlike  tuft  of  hairs  at  the  tip  of  the 


Fig.  38.    Maple  Borer,  Sesia  acerni,  adult.     About  3  times 
natural  size. 

abdomen.  The  eggs  are  laid  chiefly  in  rough  or  injured  places,  al- 
most wholly  in  the  trunk  of  the  tree,  and  not  in  its  branches.  The 
effect  of  the  injury  is  to  kill  the  bark  undermined,  and  to  enlarge 
surface  wounds  and  prevent  their  healing,  converting  them  into 
permanent,  rough,  and  very  unsightly  scars.  Sometimes  the  tree 
is  killed  by  a  girdling  of  the  trunk. 

To  prevent  attack  by  these  borers  the  tree  should  be  protected 
from  injury,  and  such  wounds  as  it  receives  should  be  painted  over 
or  covered  with  grafting  wax.  Dr.  Felt,  State  Entomologist  of 
New  York,  says  that  "the  deposition  of  eggs  could  probably  be  pre- 
vented to  considerable  extent  by  treating  the  trunks  of  trees  about 
the  middle  of  May  with  a  wash  prepared  as  follows :  Thin  one 
gallon  of  soft  soap  with  an  equal  amount  of  hot  water  and  stir  in 
one  pint  of  crude  carbolic  acid  (one-half  pint,  refined),  let  it  set 
over  night  and  then  add  eight  gallons  of  soft  water.  Apply  thor- 
oughly to  the  trunk,  especially  about  all  crevices  and  wounds,  from 
the  ground  to  about  six  or  eight  feet  high,  and  renew  if  necessary 
before  the  middle  of  June."  As  the  borers  work  near  the  surface, 
they  can  be  easily  dug  out  and  destroyed  in  fall. 


191 1]       IMPORTANT   INSECTS   OF   ILLINOIS    SHADE   TREES   AND   SHRUBS  499 

THE  NINEBARK  BORER 
(Sesia  scititla  Harris) 

Dogwood  and  ninebark  shrubs  (Cornus  sp.  and  Opulaster  opuli- 
folins)  in  the  Chicago  parks  are  generally  infested,  and  often  seri- 
ously injured,  by  a  boring  01  girdling  caterpillar  (Fig.  39)  which 
works  just  beneath  the  bark,  mainly  at  the  junction  of  the  branches 


Fig.  39.     Ninebark  Borer,  Sesia  scitula  larva. 
About  3  times  natural  size. 

or  in  the  neighborhood  of  an  old  dormant  bud.  The  burrows  of  the 
borer  sometimes  extend  lengthwise  of  the  branch,  and  sometimes 
girdle  it  near  its  origin.  In  1908  nearly  every  shrub  of  the  ninebark 
in  Washington  Park  was  infested,  and  many  of  the  branches  were 
killed  by  this  larva.  The  species  also  infests  the  chestnut,  and  has 
been  bred  from  galls  on  twigs  of  the  oak. 

The  creamy  white  larva,  half  an  inch  long  in  September,  passes 
the  winter  in  its  burrows,  and  emerges,  according  to  our  observa- 
tions, in  late  June  or  in  July.  The  head  is  brown,  darkening  almost 
to  black  towards  the  mandibles.  The  prothorax  is  slightly  brownish, 
with  two  oblique  brown  markings  on  its  posterior  half.  The  re 


Fig.    40.    Nitrebark  Borer.  Se»ia  scitttla.  adult  female. 
About  3  times  natural  size. 

maining  segments  are  creamy  white,  except  the  last,  which  is  pale 
reddish-brown. 

The  winged  insect  (Fig.  40)  is  deep  blue-black  on  the  thorax 
and  abdomen,  the  former  with  a  yellow  line  and  a  yellow  patch  on 
each  side,  and  the  latter  with  a  yellow  line  at  its  base  and,  in  the 


500 


BULLETIN  No.  151 


[October, 


male,  a  narrow  yellow  ring  on  the  second  and  fourth  segments, 
broadening  below  on  the  fourth  to  cover  the  whole  surface.  In  the 
female  the  fourth  segment  is  yellow  both  above  and  below.  The 
head  and  antennae  are  black,  the  femora  blue-black,  and  the  tibiae 
yellow.  The  fore  wings  are  transparent,  except  the  borders  and 
the  discal  mark,  which  are  blue-black.  The  outer  margin  is  marked 
with  yellow  rays.  The  hind  wings  are  transparent,  with  very  nar- 
row blue-black  margins.  The  spread  of  the  wings  is  from  18 — 22 
mm. 

This  insect  can  evidently  best  be  destroyed  by  cutting  out  and 
burning  infested  branches  in  winter  or  early  spring. 

THE  BAG-WORM 
(Thyridopteryx  ephemeraformis  Harris) 

One  sometimes  sees  hanging  from  the  branches  of  trees,  in  late 
summer  or  in  fall  or  winter,  especially  in  the  southern  part  of  the 
state,  rough  excrescences,  about  two  inches  long,  shaped  somewhat 
like  a  spindle  full  of  yarn,  soft  to  the  touch,  and  more  or  less  covered 
with  pieces  of  dead  leaves  which  seem  to  be  woven  into  their  web- 
like  substance  (Fig.  41,  /).  In  summer  it  may  be  further  noticed 


Fig.  41.  Bagworm.  Thyridopteryx  (phemertfformis:  a,  larva;  b 
and  c,  pupa,  side  and  back  views:  d,  aault;  e,  case  containing  the 
eggs;  /,  larva  in  case;  g,  eggs.  Natural  size.. 

that  these  spindle-shaped  sacks  can  creep  along  the  twig,  and  that 
there  projects  from  the  end  nearest  the  twig  the  head  and  front  part 
of  a  caterpillar,  the  remainder  of  which  is  enclosed  in  the  protect- 
ing bag.  In  winter  this  is  hung  to  the  tree  by  a  rather  tough  liga- 
ment composed  of  material  like  spider-web.  An  examination  of 
these  peculiar  bodies  at  that  season  will  show  either  that  they  are 


IMPORTANT   INSECTS  OF  ILLINOIS   SHADE  TREES   AND   SHRUBS 


501 


virtually  empty,  or  that  they  contain  a  mass  of  soft  yellow  eggs. 
(Fig.  41,  <?.)   ' 

The  insect  known  as  the  bag-worm,  to  which  these  constructions 
are  due,  is  in  several  respects  one  of  the  most  curious  in  Illinois. 
Altho  the  parent  form  is  a  moth,  the  female  is  wingless  and  naked 
(Fig.  41,  c),  looking  more  like  a  grub  than  a  moth,  and  the  wings 
of  the  male,  instead  of  being  covered  with  scales,  are  smooth  and 
transparent,  somewhat  like  those  of  a  wasp.  (Fig.  41,  d.}  The 
caterpillar  infests  a  considerable  variety  of  both  fruit  and  shade 
trees,  including  among  the  latter  evergreens  (especially  red  cedar 
and  arbor-vitae,  Fig.  42)  and  several  kinds  of  deciduous  trees. 


Fig.  42.    Bag-worm,  Thyridopteryx  ephemerceformis,  cases  hanging-  on  arbor-vitae  twig.; 
(Ohio  Experiment  Station.) 

It  does  its  injury  by  eating  the  leaves  of  trees,  and  its  numbers  are 
often  such  that  they  may  take  virtually  every  leaf  off  a  tree  of 
considerable  size. 

The  eggs,  contained  during  the  winter  in  the  bag-like  cases  on. 
the  trees,  hatch  the  following  May  or  June,  and  the  young  caterpil- 
lars begin  at  once  to  spin  for  themselves  small  conical  cases  (Fig. 
41,  g)  to  which  they  fasten  pieces  of  leaves  from  the  tree  upon 
which  they  are  feeding.  As  they  grow  these  cases  are  enlarged 
until  they  take  the  form  and  dimensions  already  described.  The 
caterpillars  (Fig.  41,  a)  travel  but  slowly,  and  seldom  leave  the 
tree  upon  which  they  were  hatched  until  they  are  about  full  grown, 


502  BULLETIN  No.   151  [October, 

when  they  are  likely  to  spin  down  and  wander  about.  They  change 
to  the  chrysalis  (Fig.  41,  fr)  within  the  bags,  which  they  fasten  to 
the  twigs  of  the  trees  as  a  preliminary,  but  the  grublike  female 
moth,  destitute  of  wings  and  with  only  minute  and  useless  legs, 
deposits  her  eggs  within  her  native  sack,  works  her  way  out  of  it, 
drops  to  the  ground  exhausted,  and  dies.  The  winged  males  (Fig. 
41,  d*)  appear  in  September  and  October,  and  soon  thereafter  the 
eggs  are  laid. 

The  bag-worm  is  a  southern  insect  in  its  general  range,  and  is 
rarely  seen  in  northern  Illinois.  It'  increases  in  importance  south- 
ward, and  in  southern  Illinois  is  often  a  troublesome  pest.  In  a 
general  trip  to  eighteen  towns,  well  distributed  thruout  the  state, 
Mr.  J.  J.  Davis,  in  1910,  found  the  bag- worm  in  four  out  of  six 
southern  Illinois  towns  visited,  but  in  no  others. 

The  simplest  method  of  destroying  these  insects  is  to  collect  the 
bags  during  the  winter  and  burn  them — a  thing  easily  done  with  the 
aid  of  pruning  shears  if  they  can  not  be  reached  by  hand.  If  this 
measure  is  neglected,  infested  trees  may  be  cleared  by  spraying  them 
with  arsenical  poisons  soon  after  the  hatching  of  the  eggs — the  latter 
part  of  June  or  early  July.  A  pound  of  arsenate  of  lead  to  forty 
gallons  of  water  is  a  safe  and  effective  poison. 

THE  POPLAR  AND  WILLOW  BORER 
(Crypt  or  hynchus  lapathi  Linn.) 

The  weeping  willow,  the  Carolina  poplar,  the  balm  of  Gilead,  and 
the  red  birch  are  ornamental  trees  of  sufficient  popularity  to  make 
the  existence  of  any  insect  pest  destructive  to  them  a  matter  of  gen- 
eral interest.  The  Carolina  poplar  especially  has  had  an  enormous 
distribution  of  late  years  in  Illinois  towns,  largely  because  of  the 
ease  and  certainty  with  which  it  may  be  raised,  and  the  rapidity  with 
which  it  grows  in  our  soils. 

The  advent  into  this  country  nearly  thirty  years  ago  of  a 
European  snout-beetle  well  known  in  the  Old  World  as  a  destroyer 
of  alders,  poplars,  and  willows,  and  occasionally  injurious  to  birches 
also,  has  seriously  endangered  our  American  plantations  of  these 
trees.  Detected  first  in  New  York  in  1882,  and  found  on  Staten 
Island  in  1886,  it  appeared  in  considerable  numbers  near  Buffalo  by 
1896,  and  the  following  year  was  reported  as  abundant  in  Boston, 
Mass.,  and  very  destructive  there  to  willows  and  poplars  of  all  kinds, 
and  to  the  red  birch.  By  1901  it  had  reached  northeastern  Ohio;  in 
1903  it  was  found  in  two  Wisconsin  nurseries;  and  in  1904  it  was  re- 
ported from  North  Dakota  in  poplars  lately  brought  into  that  state 
from  New  York.  In  Illinois  it  was  first  seen  by  us  in  1908  in  Caro- 
lina poplars  at  Chicago ;  but  once  detected  there  it  was  soon  found 
to  be  generally  distributed  and  very  destructive  to  both  poplars  and 
willows  in  all  parts  of  the  city.  (Fig.  43.)  It  has  not  yet  occurred, 


IMPORTANT    INSECTS   OF   ILLINOIS   SHADE   TREES   AND   SHRUBS 


503 


to  our  observation,  elsewhere  in  Illinois.  Wherever  it  appears  it 
multiplies  locally,  but  makes  a  slow  spread,  a  fact  apparently  due  to 
the  sluggishness  of  the  parent  beetle,  which,  although  provided  with 
wings,  makes  extremely  little,  if  any,  use  of  them.  In  consequence 


Fig.  43.  Small  poplar  tree  In  Chicago  showing  dying  of  upper 
branches  resulting  from  attacks  of  the  Poplar  and  Willow  Borer, 
Cryptorhynchus  lapat/ii. 

of  this  fact,  an  infested  grove  may  be  nearly  destroyed  before  an- 
other, near  at  hand,  becomes  even  infested.  It  extends  its  range 
most  readily  along  watercourses  by  means  of  the  willows  and  cot- 
tonwoods  with  which  our  streams  are  likely  to  be  fringed.  Its 
spread  to  distant  points  seem  to  have  been  mainly,  if  not  altogther, 
by  way  of  the  nursery  trade,  especially  that  in  poplars  and  willows 
of  various  kinds.  These  facts  make  it  particularly  important  that 


504  BULLETIN  No.   151  [October, 

the  signs  of  its  presence  should  be  generally  known,  in  order  that 
it  may  be  promptly  recognized  and  suppressed  upon  its  appearance 
in  any  new  locality. 

Injury  by  this  borer  may  be  suspected  when  the  general  health 
of  a  tree  is  evidently  affected,  where  there  are  dead  patches  of  the 
bark,  irregularly  cracked  open  (Fig.  44,  45),  or  where  openings  in 


Fig.  44.    Injury  by  Poplar  and  Willow  Borer, 
Cryptorhynchus  lapathi. 

the  bark  give  exit  to  a  soft  excrement  like  moist  sawdust  mixed 
with  fine  splinters.  The  burrows  beneath  the  bark,  made  chiefly  in 
the  cambium  layer,  are  irregular  in  direction,  sometimes  girdling  a 
small  tree,  and  show  nothing  of  the  symmetrical  pattern  made  by 
many  borers  which  undermine  the  bark.  Those  of  the  older  larvae 
dip  into  the  wood,  usually  reaching  the  center  of  the  branch  unless 
this  is  large.  These  deeper  burrows  finally  become  filled  with 
powdered  wood  and  splinters,  except  a  chamber  at  the  farther  end 
in  which  the  larva  pupates.  In  the  active  boring  stage  these  in- 
sects are  soft,  yellowish,  fleshy,  cylindrical,  footless  grubs  (Fig. 
46)  with  a  pale-brown  head  and  darker  mouth-parts.  They  are 
half  an  inch  long  when  they  reach  full  size,  which  is  about  the  last 
of  June  for  those  most  advanced.  At  this  time,  however,  young 
larvae  may  be  found  under  the  bark  down  to  a  fifth  of  an  inch  in 
length. 

The  adult  beetles  (Fig.  47)  begin  to  appear  in  July,  and  con- 
tinue abroad  at  least  until  October.  They  are  well  marked  and 
easily  distinguished  insects,  a  little  more  than  a  quarter  of  an  inch 


i9ii]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE  TREES   AND    SHRUBS  SOS. 

long,  thick-bodied,  with  a  roughened  and  punctured  surface,  and  a 
stout  curved  beak  projecting  downward  from  the  head.  The  gen- 
eral color  is  dark  sooty  brown,  more  or  less  specked  and  spotted 


Fig.  46.    Poplar  and  Willow  Borer,  Crypto- 
rhynchus  lapathi,  larva.  About  4  times  natural 

size. 


Fig.  45.    Injury  by  Poplar  and  Wil- 
low Borer,  Cryptorhynchus  lapathi. 

with  gray,  and  there  is  a  very  conspicuous  large  patch  of  light  gray 
on  the  hinder  end  of  the  wing-covers,  contrasting  strongly  with  the 
adjacent  colors.  The  sides  of  the  prothorax  are  gray,  and  there  is 
a  pair  of  rather  definite  oblique  gray  marks  just  behind  the  front 
outer  angle  of  each  wing-cover.  The  beetle  is  slow  and  lumbering 
in  its  movements,  and  when  disturbed  drops  to  the  ground  like  a 
curculio,  without  attempting  to  fly.  It  feeds  upon  the  cambium 
layer  of  the  younger  branches,  which  it  reaches  by  puncturing  the 
bark  with  its  snout.  It  lays  its  eggs  in  the  older  bark,  mainly  of 
branches  from  two  to  four  years  old.  This  the  female  does  by 
first  eating  downward  into  the  bark  by  means  of  the  jaws  at  the 
tip  of  her  snout,  taking  half  an  hour  or  more  to  hollow  out  a  cav- 
ity in  which  the  egg  is  concealed.  She  then  turns  end  for  end,  and 
leaves  an  egg  in  the  chamber  thus  made,  and  presently  moves  away 
to  repeat  the  process  at  another  point. 

The  young  hatch  mainly  in  August  and  September,  penetrate  at 
once  to  the  cambium  layer,  and  hibernate  there  while  most  of  them 
are  still  very  small.  The  following  spring  they  continue  to  work  in 
the  cambium  until  nearly  ready  for  pupation,  when  they  enter  older 
wood. 


506  BULLETIN  No.   151  [October, 

The  dependence  of  the  beetle  for  food  upon  the  bark  of  the  tree 
which  it  infests  has  suggested  the  use  of  poisons  for  its  destruction, 
and  some  tests  made  at  the  New  York  Agricultural  Experiment 
Station  show  that  the  ordinary  arsenical  poisons  applied  as  a  spray 
will  destroy  it.  Arsenate  of  lead  is  the  best  of  these  for  the  pur- 
pose, because  of  its  adhesive  quality.  Trees  to  be  protected  should 
be  thoroly  sprayed  at  intervals  of  about  a  fortnight,  beginning 


Fig.  47.  Poplar  and  Willow  Borer, 
Cryp'Oi  hynchus  lapathi,  adult.  Length, 
about  one-fourth  men. 

with  the  middle  of  July  and  continuing  thru  August.  Moder- 
ately infested  trees  may  be  saved  by  cutting  out  the  grubs  and  cov- 
ering the  wound  with  tar.  Badly  infested  trees  should  be  taken  out 
and  burned,  either  during  the  winter  or  before  July  I  of  the  follow- 
ing season.  Nursery  trees  infested  by  this  insect  should  be  un- 
hesitatingly destroyed,  since  they  are  far  worse  than  worthless,  and 
are  the  principal  means  of  conveying  the  species  to  places  not  pre- 
viously infested  by  it. 

THE  DOGWOOD  TWIG-GIRDLER 
(Oberea  tripunctata  Swederus) 

Among  the  insects  whose  nice  and  elaborate  instincts  connected 
with  the  placing  of  their  eggs  are  the  wonder  of  entomologists,  we 
must  class  the  twig-girdlers,  for  their  careful  preliminary  opera- 
tions are  such  as  to  suggest  a  knowledge  of  vegetable  physiology 
and  a  prevision  of  the  possible  difficulties  in  the  way  of  the  de- 
velopment of  their  young  certainly  quite  beyond  the  powers  of 
insect  intelligence,  and  an  unsolved  puzzle  if  regarded  as  a  product 


IMPORTANT   INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS 


507 


of  natural  selection.     The  twig-girdler  of  the  dogwood  is  an  ex- 
ample. 

This  is  a  small,  cylindrical  beetle  (Fig.  48),  about  half  an  inch 
long  and  less  than  an  eighth  of  an  inch  in  diameter,  which  prepares 
a  chosen  twig  for  the  reception  of  the  egg  by  first  cutting  a  groove 
around  it  a  few  inches  from  its  tip  in  such  a  way  that  the  twig 


Fig  48.  Dogwood  Twig-gird- 
ler, Oberea  tripunctata,  adult. 
About  5  times  natural  size. 

Fig.  49.  Cornus  twig 
g i  r  d 1 e  d  by  Dogwood 
Twig-girdler,  Oberta  tri- 
punctata, and  part  en- 
larged, showing  egg  in 
position. 

presently  breaks  off  at  this  point,  and  afterwards  making  a  second 
girdle,  not  so  deep  as  the  firsthand  from  two  to  four  inches  farther 
back.  (Fig.  49.)  It  then  makes  two  parallel  cuts,  about  half  an 
inch  long,  lengthwise  thru  the  bark  between  the  two  girdling  in- 
cisions, and  at  the  proximal  end  of  these  makes  a  short  transverse 
slit  in  a  way  to  form  an  angular  flap,  beneath  which  it  pushes  its 
egg.  The  effect  of  all  this  surgery  must  be  to  stop  the  growth  of 
that  part  of  the  branch  operated  on,  and  to  check  the  flow  of  sap 
to  the  section  in  which  the  egg  is  laid. 


508 


BULLETIN  No.  151 


[October, 


These  operations  are  distributed,  in  northern  Illinois,  over  the 
month  between  the  middle  of  June  and  the  middle  of  July.  The 
eggs  hatch  within  a  week  or  ten  days,  and  the  young  larvae  pene- 
trate the  twig,  burrowing  downwards  towards  its  point  of  attach- 
ment, and  making  holes  to  the  surface  at  intervals  thru  which  to 
discharge  their  excrement.  After  a  time  the  larva  cuts  off,  from 
within,  the  part  of  the  twig  thru  which  it  has  made  its  way,  and 
plugs  the  open  end  of  the  burrow  with  coarse  bits  of  frass.  It  oc- 
casionally repeats  this  plugging,  pursuing  its  way  until  winter 
overtakes  it,  and  pupating  within  its  burrow  from  the  middle  to  the 
latter  part  of  the  following  May,  first,  however,  commonly  cutting 
off  the  branch  obliquely  and  plugging  the  cavity  a  little  beyond  its 
pupal  cell.  (Fig.  50,  51.)  The  adult  emerges  during  the  latter 


Fig.  50.  Dogwood  Twig 
girdler,  Oberea  tripunc 
fata,  larva.  About  4 
times  natural  size. 


Fig.  51.  Cornus  twig 
with  burrow  of  Dog- 
wood Twig-girdler,  Obe- 
rea tripunclata:  a,  end 
obliquely  cut  off  by 
larva;  6,  /,  plugs  of 
trass;  c,  openings  made 
by  larva  and  plugged 
up  later;  d,  cocoon  of 
icnneumoned  parasite; 
e,  remains  of  parasitized 
Oberea  larva. 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS 


509 


half  of  June,  eats  its  way  thru  this  terminal  twig,  and  feeds  dur- 
ing its  short  life  on  the  leaves  of  the  infested  tree,  making  oval 
holes  thru  the  leaves  along  the  course  of  the  veins.  (Fig.  53.) 

The  presence  of  this  borer  is  commonly  first  betrayed  by  a  with- 
ering of  the  leaves  at  the  tip  of  the  girdled  shoots.  It  is  a  rather 
common  pest  in  the  Chicago  parks,  where  it  has  often  been  abun- 
dant enough  on  the  red-osier  dogwood  (Cornus  sanguined}  to  be 
decidedly  injurious.  Like  the  other  small  twig-girdlers,  this  species 
can  best  be  destroyed  by  cutting  off  and  destroying  the  affected 


Fig.  52.  Dogwood  Twig- 
girdler,  Oberea  tripunctata, 
pupa.  About  zys  times 
natural  size. 


Fig.  53.  Cornus  leaf  injured  by 
feeding  of  adult  Dogwood  Twig- 
girdler,  Oberea  tripunctata. 


branches  at  a  time  when  they  are  certain  to  contain  the  borer;  that 
is  to  say,  in  this  case,  in  any  month  except  June  and  July. 

The  various  species  of  this  genus  have  been  so  imperfectly  dis- 
tinguished that  a  specific  description  of  this  will  not  be  attempted 
here;  but  the  reader  is  referred  to  the  illustrations  for  its  general 
characters.  Its  larva  is  much  subject  to  destruction  by  parasites; 
and  a  characteristic  parasitic  species  has  been  repeatedly  bred  by 
us  from  infested  twigs. 


510 


BULLETIN  No.   151 


[October, 


THE  LOCUST  BORER 
(Cyllene  robinice  Forst.) 

A  great  obstacle  to  the  growth  of  the  common  black  locust  as 
a  timber  tree  in  Illinois  has  been  the  work  of  a  borer  which  in- 
fests this  tree  only,  multiplying  year  after  year  in  a  locust  grove 
until  it  destroys  every  tree.  It  was  a  common  practice  in  the  early 
settlement  of  the  northern  part  of  the  state  for  the  farmers  to  plant 
a  grove  of  locusts,  with  a  view  especially  to  a  supply  of  fence-posts. 
These  groves  were,  however,  all  destroyed  by  this  borer  during  the 
middle  part  of  the  nineteenth  century,  and  the  planting  of  this 
tree  was  universally  abandoned  at  that  time.  Of  course,  with  the 
disappearance  of  the  tree  the  borer  likewise  disappeared,  and  the 
growing  of  the  locust  is  now  again  possible  if  due  precautions  be 
taken  against  its  destruction  by  this  insect.  Fortunately,  the  recent 
work  of  Dr.  A.  D.  Hopkins,  in  charge  of  forest  insect  investigations 
for  the  United  States  Department  of  Agriculture,  has  made  it  per- 
fectly feasible  to  grow  locusts  with  little  or  no  loss  from  this  cause, 
and  the  following  account  is  mainly  taken  from  his  publications  on 
this  subject. 

The  first  evidence  of  attack  by  this  borer  in  spring  is  a  fine 
brownish  dust  and  an  oozing  of  sap  from  the  bark.  Later,  gumlike 
exudations  appear  on  the  injured  spots,  and  quantities  of  yellowish 


Fig.  54.  Locust  Borer.  Cyller,e  robinice;  pupa:  a,  front  view 
b,  back  view.  Enlarged  as  indicated.  (D.  S.  Dept.  of  Agri 
culture.) 


/9//]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND  SHRUBS 


511 


dust  lodge  in  the  forks  of  the  tree  or  branches,  and  in  the  loose  bark 
on  the  trunk  and  around  its  base.  Badly  infested  trees  show  a 
dwarfed,  faded,  or  sickly  foliage  about  the  middle  of  May,  and 
many  of  the  leaf  buds  fail  to  open.  The  author  of  this  injury  is 
a  whitish,  thick-bodied,  distinctly  segmented,  seemingly  footless 
grub,  nearly  an  inch  long  when  full  grown,  with  small  head,  and  only 
a  pair  of  minute  feet  on  the  next  segment  behind.  It  hatches  from 
eggs  laid  in  crevices  of  the  bark  from  August  to  October.  The 
young  borers  are  still  very  small  when  the  winter  overtakes  them, 
and  they  hibernate  in  small  cavities  made  by  them  in  the  outer  bark 
of  the  trunk  and  branches.  They  commence  operations  when  the  sap 
of  the  tree  begins  to  flow  the  following  spring,  and  presently  pene- 
trate the  wood,  burrowing  actively  about  until  July  or  August,  in 
central  Illinois,  when  they  begin  to  change  to  the  pupa  (Fig.  54), 
to  emerge  about  a  month  later  in  the  beetle  stage  (Fig.  55). 


Fig.  55.    Locust  Borer,    Cyllene  robinice:    a,  male;    b.  female.     Enlarged  as 
indicated.    (U.  S.  Dept.  of  Agriculture.) 

The  adult  is  a  very  showy,  elongate,  brown  beetle,  five-eighths  to 
three-fourths  of  an  inch  in  length,  conspicuously  marked  with  three 
straight  bands  of  bright  yellow  across  the  thorax  and  five  broken  or 
irregular  bands  of  the  same  color  across  the  wing-covers.  There  is 
also  a  bright  yellow  patch  on  the  upper  side  of  the  tip  of  the  ab- 
domen. The  beetles  are  to  be  found  in  September,  and  occasionally 
in  early  October,  on  locust-trees,  and  on  various  species  of  golden- 
rod,  upon  the  flowers  of  which  they  feed.  Now  and  then  a  speci- 


512  BULLETIN  No.  151  [October, 

men  may  survive  the  winter  and  be  taken  abroad  in  April,  or  even 
in  May. 

From  the  foregoing  statements  it  is  evident  that  the  time  of  cut- 
ting trees,  whether  to  thin  the  grove  or  for  commercial  use,  is  an 
important  item  in  the  control  of  this  beetle.  All  such  cutting  should 
be  done  between  October  i  and  April  i,  care  being  taken  that  all 
trees  showing  the  presence  of  the  borer  are  selected  for  removal. 
The  bark  should  then  be  taken  off,  and  the  brush  and  rubbish  should 
be  burned.  Simply  to  kill  the  larvae  and  borers  in  badly  infested 
and  damaged  trees,  these  should  be  cut  and  destroyed  in  May  and 
June,  when  their  condition  can  be  readily  detected;  but  the  work 
should  be  completed  by  the  time  the  flowers  have  all  fallen  from 
the  trees,  as  otherwise  the  borers  may  mature  and  escape.  Where 
the  beetles  are  abundant  on  the  goldenrod,  they  may  be  attracted  and 
killed,  according  to  Dr.  A.  D.  Hopkins,  by  smearing  molasses 
poisoned  with  arsenic  upon  the  trees,  due  account  being  taken  of 
the  fact  that  honey-bees  are  liable  to  destruction  by  this  poison,  and 
that  it  should  not  be  used  where  these  are  kept.  Unsuccessful  ex- 
periments were  made  by  one  of  my  assistants,  Mr.  W.  P.  Flint,  in 
1910,  with  a  mixture  of  sugar  and  vinegar,  and  another  of  sugar 
and  alcohol.  Altho  attractive  to  a  variety  of  other  insects,  the 
beetles  of  the  locust-borer  paid  no  attention  to  them.  Tanglefoot, 
on  the  other  hand,  placed  on  the  trees  September  16,  when  the 
beetles  were  freely  running  about  mating  and  laying  their  eggs, 
disabled  the  beetles  and  put  a  stop  to  their  operations. 

Highly  useful  directions  for  the  management  of  locust  plan- 
tations in  a  way  to  prevent  injury  by  borers,  are  contained  in  Bulle- 
tin 58  of  the  Bureau  of  Entomology  of  the  U.  S.  Department  of 
Agriculture,  printed  in  1910. 

THE  OAK  TWIG-PRUNER 
(Elaphidion  villosum  Fabr.) 

Among  the  more  striking  and  curious  kinds  of  insect  injury  to 
trees  are  those  which  take  the  form  of  amputation  of  twigs  and 
small  branches  during  the  growing  season — an  injury  which  seems 
purposeless  and  excessive  until  one  sees  just  how  it  benefits  the 
author  of  it. 

The  oak  twig-pruner  (Fig.  56)  is  one  of  the  best  known  Ameri- 
can insects  with  this  habit  of  injury,  affecting,  as  it  does,  a  large 
variety  of  trees  and  shrubs,  and  injuring  most  frequently  some  of 
the  commonest  and  most  useful  species.  It  is  best  known,  perhaps, 
for  its  work  on  oaks,  hickories,  and  maples,  altho  it  has  been  re- 
ported to  attack  also  apple,  peach,  pear,  plum,  quince,  locust,  redbud, 
sumach,  Osage  orange,  fir,  grape,  and  climbing  bittersweet.  In  Illi- 
nois we  have  bred  it  from  oaks,  hickories,  persimmon,  and  peach, 


191 1]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  513 

and  have  found  it  thruout  the  state.  In  parts  of  Michigan,  peach- 
trees  have  sometimes  been  nearly  destroyed  by  it,  and  an  equally  se- 
rious injury  has  been  done  by  it  in  New  York  to  pears.  In  Illinois 
we  once  found  it  at  Effingham  cutting  off  young  apples-trees  from 


Fig.  56.    Oak  Twig-pruner,  Elaphidion  villosum,  larva. 
About  5  times  natural  size. 

one  to  two  feet  above  the  groun^ ;  and  Dr.  F.  W.  Coding  reported 
it,  in  1884,  as  doing  great  damage  to  hickory  and  elm  at  Ancona,  in 
Livingston  county.  In  Pennsylvania,  oak  forests  have  been  so  in- 
fested by  it  that  carloads  of  the  twigs  might  have  been  collected 
from  under  the  trees ;  and  in  Connecticut,  hickories  have  been  so 
thoroly  pruned  that  a  barrel  of  twigs  and  branches  have  fallen 
from  a  single  tree. 

The  injury  done  by  this  insect  is  not,  however,  so  severe  as  it 
looks.  It  may  affect  considerably  the  appearance  of  young  trees, 
by  deforming  their  top;  but  large  trees  are  generally  little  harmed 
by  the  pruning  they  receive,  and  the  littering  of  lawns  with  ampu- 
tated twigs  is  at  most  an  annoyance  merely.  The  girdled  twigs  and 
branches  may  vary  in  length  from  a  few  inches  to  several  feet,  but 
Dr.  Fitch  mentions  one  that  was  ten  feet  long  and  over  an  inch 
thick.  Commonly,  however,  they  are  a  quarter  of  an  inch  or  less 
in  diameter,  and  vary  from  two  to  six  inches  in  length.  Occasion- 
ally a  single  one  will  contain  two  larvae,  the  burrows  then  running 
down  each  side  of  the  twig.  Fallen  limbs,  if  not  disposed  of,  may 
serve,  as  Chittenden  has  said,  as  breeding  places  for  various  kinds 
of  injurious  borers,  which  may  come  out  from  them  to  attack  and 
injure  living  trees. 

The  method  of  the  primer's  work  is  such  that  a  fallen  twig  is 
seen  to  have  been  hollowed  out  centrally — a  large  part  of  its  interior 
often  being  eaten  away — and  plugged  with  sawdust,  and  its  larger 
end  has  been  gnawed  off  from  within,  having  a  cut  surface  as  smooth 
as  if  made  by  a  chisel. 

The  adult  twig-pruner  is  a  rather  slender,  dark  brown  beetle 
(Fig.  57)  from  a  half  to  three-quarters  of  an  inch  in  length, 
sparsely  covered  with  coarse  white  or  yellowish  hairs  which  show 
a  tendency  to  collect  in  irregular  clumps  or  spots.  The  edge  of  the 
tip  of  each  wing-cover  is  concave  between  two  stout  sharp  spines 
or  teeth",  of  which  the  outer  is  usually  the  larger.  The  female  lays 


514 


BULLETIN  No.   151 


[October, 


her  eggs  in  the  smaller  twigs  of  living  trees,  most  commonly  in 
July.  The  young  larva  first  eats  out  the  wood  under  the  bark  in 
the  direction  of  the  grain,  packing  its  burrow  behind  it  with  its 
castings,  and  working  towards  the  base  of  the  twig.  Later  it  cuts 
holes  in  the  bark  thru  which  these  castings  are  rejected,  and 
then  follows  the  center  of  the  twig,  making  a  channel  more  or  less 
oval  in  cross-section,  corresponding  to  its  own  shape.  When  it  has 
reached  its  growth  it  begins  to  gnaw,  from  within,  a  circular  groove, 
deepening  this  until  the  twig  or  branch  is  so  weakened  at  this 


Pig.  57.    Oak   Twig-pruner,   Elaphidion   mllosum, 
adult.    About  5  times  natural  size. 

point  that  the  wind  readily  breaks  it  off,  usually  carrying  the  insect 
with  it.  Occasionally,  however,  the  larva  is  left  in  its  burrow  on 
the  tree  and  finishes  its  transformations  there.  The  value  of 
this  operation  to  the  pruner  would  seem  to  be  a  preparation  for 
the  exit  of  the  beetle,  which  originates  within  the  burrow,  but 
which  has  not  jaws  of  a  sufficient  strength  to  enable  it  to  gnaw 
its  way  out  thru  the  wood  inclosing  it.  This  explanation,  given 
by  Chittenden,  seems  at  least  to  be  the  most  reasonable  among 
several  that  have  been  proposed  to  account  for  this  curious  habit. 
After  the  twig  has  been  cut  off  the  larva  within  it  plugs  up  the 
severed  end,  changes  to  the  pupa,  and  later  to  the  beetle,  coming  out 
as  an  adult  the  following  summer. 


191 1]       IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  515 

Published  accounts  disagree  as  to  the  length  of  the  life  cycle  of 
this  species.  It  seems  to  be  a  single  year  under  the  most  favorable 
conditions,  but  capable  of  being  lengthened  to  two  or  even  three 
years,  particularly  if  the  branch  dies  before  the  larva  is  full  grown. 

As  nearly  all  the  borers  pass  the  winter  in  the  fallen  twigs,  it 
easily  follows  that  their  injuries  may  be  readily  arrested  by  gather- 
ing these  up  and  burning  them  in  winter  or  in  spring.  This  effec- 
tive measure  is  so  simple  and  so  easily  applied  that  no  other  seems 
necessary. 

THE  BRONZE  BIRCH-BORER 
(Agrilus  anxius  Gory) 

This  insect  is  a  deadly  pest  of  the  birches,  especially  of  the  beau- 
tiful and  popular  white  birch,  which  it  is  quite  capable  of  extermin- 
ating locally  if  its  presence  is  not  early  detected  and  if  prompt  meas- 
ures are  not  then  taken  for  its  destruction.  As  an  infested  tree  is  not 
likely  to  last  more  than  two  or  three  years,  the  necessity  of  energetic 
measures  is  obvious.  Unfortunately,  this  insect  does  not  usually 
make  conspicuous  local  marks  of  the  injury  it  is  doing,  and  the 
earliest  sign  of  its  presence  is  often  the  death  of  one  or  more 
branches  in  the  top  of  the  tree.  If  a  birch  is  seen  to  be  dying  at  the 
top  it  should  at  once  be  examined  for  evidences  of  the  presence  of 
this  borer,  since  in  some  cases  this  condition  may  be  due  to  drought 
or  other  general  causes.  If  the  bronze  borer  be  the  cause,  the  fact 
may  be  ascertained  by  lifting  the  bark  from  dead  branches  which 
are  not  yet  dry,  or  from  the  more  unhealthy  looking  spots  on  the 
living  parts  of  the  tree.  If  the  insect  be  present,  its  tortuous  or 
zigzag  burrows  will  be  noticed,  and  further  search  will  disclose  the 
borer  itself  in  one  or  more  of  its  stages  of  larva,  pupa,  or  adult. 
Sometimes,  indeed,  its  presence  is  shown  by  a  ridged  appearance  of 
the  bark,  the  ridges  running  crosswise  of  the  branches  or  in  a  more 
or  less  spiral  direction.  Peculiar  rusty  or  reddish  spots  may  also  be 
seen  on  the  larger  branches  or  on  the  trunk  where  the  bark  has  been 
undermined  by  the  interlacing  burrows  of  the  borer.  Often  branches 
weakened  by  the  borers  and  by  consequent  decay  of  the  wood,  break 
at  the  point  of  injury,  either  hanging  down  or  falling  from  the 
tree.  This  appearance  is  rather  characteristic  of  the  work  of  the 
borers,  and  may  serve  to  distinguish  an  infested  tree  from  a  "stag 
head,"  due  to  drouth. 

In  its  destructive  stage  this  insect  is  a  small,  flattened,  footless, 
creamy  white  grub  about  three-fourths  of  an  inch  long  when  full 
grown,  with  dark  mouth-parts  and  a  small  head  which  is  partly 
drawn  back  into  the  broad,  flat,  pale  brownish,  first  segment  of  the 
body.  At  the  opposite  end  is  a  pair  of  minute  forceps-like  spines, 
brown  and  hornlike,  with  two  teeth  on  the  inner  edge  of  each.  In 
this  larval  condition  the  borer  may  be  found  in  its  burrows  beneath 


516 


BULLETIN   No.   151 


[October, 


the  bark  at  any  time  during  fall,  winter,  and  early  spring.  If  the 
tree  has  been  long  infested,  the  bark  is  usually  perforated  by  small 
roughly  semicircular  holes  about  twice  the  diameter  of  the  head  of 
an  ordinary  pin.  (Fig.  58.)  These  holes  are  made  by  the  beetles 
when  they  come  out  in  May  and  June  for  their  brief  life  in  the 
open  air. 

The  beetle  (Fig.  59)  is  a  hard,  small,  bronze-green  or  violet  in- 
sect, varying  somewhat  in  size,  but  approximately  half  an  inch  long 
or  a  little  less.  It  is  shining  but  minutely  punctured  under  a  glass, 


Fig.  58.  Exit  holes  of  the  Bronze  Birch-borer,  Agrilus 
anxius,  in  the  bark.  Natural  size.  (Cornell  Experiment 
Station.) 


-  Fig.  59.  Bronze  Birch-borer,  Agrilu 
anxius,  adult.  About  5  times  natura 
size. 


with  the  sides  nearly  parallel,  tapering  conspicuously  behind  to  a 
blunt  tip,  notched  where  the  rounded  ends  of  the  wing-covers  come 
together. 

Altho  most  notorious  for  its  injury  to  the  white  birch,  es- 
pecially the  cut-leaved  variety,  it  infests  all  the  birches.  It  is  the 
most  destructive  enemy  of  these  trees  in  the  Chicago  parks,  thru 
which  it  is  generally  distributed.  It  is  especially  dangerous  because 
there  is  no  means  of  destroying  it  which  does  not  involve  also  the 
destruction  of  the  infested  tree.  It  is  a  saddening  conclusion  which 
is  forced  upon  the  owner  of  a  beautiful  birch  infested  by  this  borer, 
that  the  tree  is  doomed,  and  that  the  only  means  of  saving  other 
trees  in  its  neighborhood  is  to  cut  it  close  to  the  ground  in  winter  or 
spring,  as  early  as  the  first  of  May,  and  to  burn  it,  trunk  and 
branches,  before  the  beetles  can  emerge  to  lay  their  eggs  elsewhere. 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  517 

The  larvae  hatch  in  June,  and  possibly  also  in  July,  from  eggs 
laid  in  crevices  in  the  rougher  places  of  the  bark.  They  bore 
thru  the  bark  at  once  and  begin  to  mine  in  the  sapwood,  some- 
times dipping  inward  to  the  older  wood  or  even  penetrating  to  the 
center  of  a  small  branch.  The  irregular  mine  is  always  packed  with 
the  castings  of  the  grub,  and  increases  in  diameter,  of  course,  as 
the  latter  grows,  measuring  at  the  largest  about  an  eighth  of  an  inch 
across.  Here  the  borer  lives  in  the  larval  state  until  the  latter  part 
of  the  following  April  or  early  May,  when  it  begins  to  transform 
within  its  burrow  to  the  pupa  stage,  and  within  another  month  to 
the  beetle.  This  escapes  from  the  tree  from  the  middle  to  the  last 
of  June  in  northern  Illinois,  by  gnawing  through  the  bark,  flies 
abroad  to  feed  on  the  leaves  of  trees,  and  soon  pairs  and  lays  its 
eggs.  Curiously,  it  seems  to  feed  but  little  on  the  birch,  preferring 
the  leaves  of  poplar,  willow,  and  elm  to  those  of  its  native  tree. 
There  is,  indeed,  some  evidence  that  it  infests  the  willow,  producing 
gall-like  swellings  on  the  twigs,  but  the  identity  of  the  species  to 
which  this  injury  is  referred  is  not  positively  settled. 

Trees  of  large  size  are  often  killed  by  this  borer  within  three  or 
four  years  after  they  first  become  infested,  and' few  live  more  than 
two  or  three  years  after  the  top  branches  begin  to  die.  The  neces- 
sity of  prompt  action  is  thus  manifest,  and  as  the  time  of  the  escape 
of  the  beetles  varies  with  latitude  and  the  weather  of  the  year,  it  is 
best  to  take  time  by  the  forelock  and  to  destroy  the  infested  tree 
as  early  at  least  as  April  i.  Then  one  may  be  sure  that  nothing  can 
have  escaped  from  it  to  extend  the  injury. 

This  insect  is  not  now  known  to  range  beyond  Virginia  to  the 
south  or  Illinois  to  the  west,  but  it  very  likely  occurs  wherever 
birches  are  grown.  We  have  lately  found  it  (1910)  outside  Chi- 
cago, in  Elgin,  Rock  Island,  Moline,  and  Bloomington,  abundant 
enough  in  all  these  places  to  be  decidedly  injurious  to  the  birches. 
It  has  been  quite  fully  discussed  by  Professor  M.  V.  Slingerland  in 
Bulletin  234  of  the  Cornell  University  Agricultural  Experiment 
Station,  published  in  January,  1906,  and  briefer  accounts  may  be 
found  in  the  report  of  Dr.  E.  P.  Felt,  State  Entomologist  of  New 
York,  in  "Insects  Affecting  Park  and  Woodland  Trees"  (page 
284),  published  in  1905 ;  in  an  article  by  F.  H.  Chittenden  published 
in  1898  in  Bulletin  18,  new  series,  of  the  Division  of  Entomology, 
U.  S.  Department  of  Agriculture;  and  in  a  paper  on  "A  Disease 
of  the  White  Birch,"  by  John  Larsen,  printed  by  the  Michigan 
Academy  of  Science  in  its  third  report  (1902). 

THE  SCURFY  SCALE 
(Chionaspis  furfur  a  Fitch) 

The  so-called  scurfy  scale  is  the  commonest  of  all  scale  insects 
thruout  the  state  on  shade  and  orchard  trees.  The  female  scale 


518  BULLETIN  No.   151  [October, 

(Fig.  60,  a,  c)  is  about  a  tenth  of  an  inch  in  length,  irregularly 
oval,  with  a  yellowish  point  at  one  end,  and  but  very  slightly  con- 
vex. It  is  nearly  white  when  fresh,  but  becomes  gray  or  sooty 
with  exposure.  The  scale  of  the  male  insect  (Fig.  60,  b,  d)  is 


Fig.  60.  Scurfy  Scale,  Chionaspig  furfura: 
a,  b.  female  and  male  scales,  natural  size;  c, 
d,  same,  enlarged. 

narrow,  with  sub-parallel  sides,  and  is  marked  by  three  longitudinal 
ridges.  The  species  may  be  readily  recognized  in  winter  by  the 
fact  that  under  each  female  scale  will  be  found  a  small  mass  of 
minute,  purplish  eggs.  The  young  appear  to  the  naked  eye  as 
active,  snowy  whitish  or  reddish  specks.  These  insects  are  often 
so  abundant  on  an  infested  tree  as  to  give  a  scurfy  appearance  to 
the  trunk  and  limbs. 

This  scale  insect  is  a  general  feeder,  but  is  especially  common 
on  rosaceous  plants.  It  also  heavily  infests  the  elm,  which  seems  the 
most  susceptible  to  its  injuries  of  any  of  our  ordinary  shade  trees. 
The  red-twigged  dogwood  is  often  incrusted  by  it,  and  the  moun- 
tain ash,  hawthorn,  pear,  and  currant  are  sometimes  attacked.  The 
scurfy  scale  winters  in  the  egg,  and  hatches,  with  us,  during  the 
latter  half  of  May — earlier  or  later  according  to  the  season  and  the 
part  of  the  state.  In  central  and  southern  Illinois  eggs  are  laid 
for  a  second  generation,  the  date  of  which,  however,  has  not  been 
accurately  determined.  Altho  this  can  not  be  classed  among  the 
more  destructive  scale  insects,  it  is  nevertheless  injurious  where  es- 
pecially abundant,  checking  the  growth  and  diminishing  the  vitality 
of  the  infested  tree  or  shrub  in  a  way  to  make  it  less  presentable  and 
more  susceptible  to  the  attacks  of  other  insects  and  of  disease. 

Two  insecticide  sprays  are  fairly  effective  against  this  insect; 
one  a  winter  spray  of  lime  and  sulphur,  prepared  and  administered 
as  described  in  detail  under  the  article  concerning  the  San  Jose 
scale,  and  the  other  a  summer  spray  of  kerosene  emulsion,  a  formula 


IMPORTANT    INSECTS   OF    ILLINOIS    SHADE   TREES    AND    SHRUBS 


519 


for  the  preparation  of  which  is  given  tinder  the  cottony  maple  scale. 
The  lime-sulphur  mixture  should  be  applied  as  late  in  the  winter  as 
practicable,  best  just  before  the  opening  of  the  leaves  in  spring.  The 
kerosene  emulsion  must  be  applied  immediately  after  the  hatching 
process  is  virtually  complete,  a  point  which  can  only  be  determined 
accurately  by  careful  observation.  If  the  young  are  allowed  to  live 
too  long  they  become  covered  and  protected,  after  fixing  themselves, 
by  a  waxy  scale  which  the  emulsion  will  not  penetrate.  It  should  be 
applied  in  a  strength  to  contain  ten  percent  of  kerosene.  Dr. 
James  Fletcher,  Dominion  Entomologist,  Canada,  recommended 
spraying  infested  trees  with  a  whitewash  made  by  slaking  a  pound 
of  lime  to  the  gallon  of  water,  one  such  application  to  be  made  in 
fall  as  soon  as  the  leaves  have. fallen,  and  a  second  immediately  after 
the  first  has  dried.  This  is  said  to  loosen  the  hibernating  scales, 
which  subsequently  fall  from  the  tree  with  the  dried  whitewash. 

THE  OYSTER-SHELL  SCALE 
(Lepidosaphes  ulnii  Linn.) 

The  oyster-shell  scale  is  among  the  more  conspicuous  and  easily 
recognized  of  the  smaller  scale  insects  of  our  trees  and  shrubs,  the 


Fig.  61.  Oyster-shell  Scale,  Lepidosaphes  ulmi:  a.  female  scale, 
under  side,  showing  insect  and  its  eggs  within;  b,  same,  from 
above;  c,  same,  natural  size;  d,  e,  male  scale,  enlarged  and 
natural  size. 


520  BULLETIN  No.   151  [October, 

common  name  suggesting  its  most  conspicuous  character.  It  has, 
indeed,  the  convex,  elongate,  and  more  or  less  bent  and  irregular 
form  of  an  oyster  shell.  The  female  scales  (Fig.  61,  a,  b,  c}  are 
about  an  eighth  of  an  inch  long,  the  male  scales  (Fig.  61,  d,  e) 
smaller,  with  a  little  hinge  or  flap  behind,  thru  which  the  winged 
males  escape  when  mature.  The  scale  is  usually  brown  to  dark 
brown  in  color,  tho  occasionally  bleached  to  gray  by  exposure 
to  the  winter  weather.  The  eggs  of  the  species  hatch  in  Illinois 
shortly  after  the  time  the  apple  blossoms  fall.  Each  female  scale 
has  during  the  winter  from  fifty  to  a  hundred  and  twenty-five  pale 
yellowish  eggs  beneath  it,  from  which  the  young  emerge  during 
the  latter  part  of  May  or  the  first  of  June.  A  second  generation 
occurs  in  central  and  southern  Illinois  early  in  July.  The  young 
are  able,  at  first,  to  crawl  about  somewhat  actively,  and  it  is 
principally  by  this  means  that  the  species  is  distributed,  altho  it 
may  be  conveyed  to  distant  points  upon  infested  nursery  stock. 
The  scale  insect  is  both  larger  and  more  injurious  than  the  scurf} 
scale,  and  infests  also  a  larger  variety  of  trees  and  shrubs.  Elm, 
poplar,  willow,  horse-chestnut,  lilac,  red-twigged  dogwood,  and 
currant  are  among  those  most  frequently  and  seriously  injured. 

The  treatment  for  this  scale  is  identical  with  that  described  in 
the  article  for  the  scurfy  scale,  just  preceding. 

THE  SAN  JOSE  SCALE 
(Aspidiotus  perniciostis  Comst.) 

This  notorious  and  destructive  pes.t  is  much  less  injurious  to 
ornamental  vegetation  than  to  fruit  trees  and  shrubs,  but  is  never- 
theless decidedly  harmful  to  several  of  the  former,  particularly  to 
those  belonging  to  the  family  of  roses.  It  is  also  very  injurious  to 
the  mountain  ash,  but  the  Japanese  quince  (Pyrus  japonica)  is  the 
common  shrub  most  likely  to  betray  its  presence. 

It  is  a  circular,  grayish  or  yellowish,  scale  insect  about  one- 
sixteenth  of  an  inch  in  diameter,  but  slightly  convex,  and  marked 
by  a  central  nipple  and  one  or  two  surrounding  circular  ridges.  It 
is  an  inconspicuous  object,  but  is  recognizable  by  the  appearance 
which  it  gives  to  a  badly  infested  bark  (Fig.  62),  which  it  covers 
with  dark  gray  patches  of  a  continuous  grayish  crust,  which  exudes, 
when  crushed  with  the  finger-nail,  an  oily,  yellowish  substance  due 
to  the  pressure  on  the  living  insects  under  the  scales.  The  bark  of 
a  tree  but  sparsely  infested  may  be  seen,  on  close  examination,  to 
be  irregularly  specked  with  small  circular  granules  which  give  it  an 
unhealthy  look.  The  surface  immediately  beneath  the  living  scales 
often  shows  a  reddish  discoloration;  and  on  the  leaves  and  green 
twigs  are  more  conspicuous  red  blotches  which  surround  the  scales. 


IMPORTANT   INSECTS  OF   ILLINOIS   SHADE  TREES   AND   SHRUBS  521 

The  largest  scales  are  about  the  size  of  the  head  of  an  ordinary 
pin,  and  the  smallest  ones  are  mere  specks  on  the  twig. 

This  insect  passes  the  winter  partly  grown,  reaches  its  full  size 
in  spring,  and  begins  to  bring  forth  its  living  young  about  the  first 
of  June,  in  average  years,  in  the  central  part  of  Illinois.  These  may 
be  seen  as  minute  yellow  specks  wandering  over  the  surface  in  search 
of  a  suitable  place  to  establish  themselves.  This  period  of  active 
life  is  often  limited  to  a  few  hours,  and  at  most  to  one  or  two  days. 
Three  or  four  generations  are  bred  in  a  single  season. 


Fig.  62.  San  Jose  Scale,  Aspidiotus 
perniciows.  Natural  size.  (Connec- 
ticut Experiment  Station.) 

It  has  been  found  commonly  infesting  and  often  injuring  more 
than  seventy  trees  and  shrubs,  and  occasionally  nearly  as  many 
more.  The  commoner  kinds  coming  under  the  former  list  are  some 
of  the  dogwoods,  the  hawthorns  (Cratcegus},  the  quinces,  the  pop- 
lars, the  cherries  and  pears,  currants  and  gooseberries,  roses,  willows, 
mountain  ash,  snowberry,  lilac,  basswood,  Osage  orange,  and  the 
elms.  Those  less  seriously  infested  are  the  maples,  horse-chestnut, 
Virginia  creeper,  the  birches,  chestnut,  catalpa,  hackberry,  the  flow- 
ering and  other  dogwoods,  the  persimmon,  Forsythia,  white  ash, 


522  BULLETIN   No.   151  [October, 

honey-locust,  Althea,  pecan,  black  walnut,  mountain  laurel,  honey- 
suckle, mulberry,  white  spruce,  sour  cherry,  sumach,  smoke-bush, 
locust,  raspberry  and  the  blackberry,  elder,  sassafras,  various  species 
of  Spiraa,  arbor-vitae,  Viburnum,  and  grape.  Popular  species  not  in- 
fested by  it  are  Ailanthus  or  tree  of  heaven,  papaw,  spice-bush,  bar- 
berry, trumpet-vine,  the  hornbeams,  cedar,  bittersweet,  buttonbush, 
Judas-tree,  fringe-tree,  pepperbush,  leatherwood,  gingko,  Kentucky 
coffee-tree,  witch-hazel,  English  ivy,  hickories  except  the  pecan, 
hydrangeas,  yellow  jasmine,  butternut,  juniper,  larches,  sweet  gum, 
tulip-tree,  matrimony-vine,  wax  myrtle,  black  gum,  syringa,  pine, 
sycamore,  the  oaks,  the  rhododendrons,  bald  cypress,  trumpet- 
creeper,  blueberry,  hemlock,  Wistaria,  and  prickly  ash.  The  last 
list  is  especially  important  in  Illinois,  thruout  which  the  San  Jose 
scale  is  certain  ultimately  to  become  generally  distributed,  because 
it  includes  a  large  and  varied  list  of  ornamentals  from  which  selec- 
•tions  may  be  made  without  the  risk  of  loss  or  injury  by  this  most 
destructive  pest. 

The  San  Jose  scale  is  conveyed  to  distant  points  mainly  by 
the  trade  in  nursery  stock,  and  otherwise  it  spreads  only  by  means 
of  the  minute  crawling  young.  Its  means  of  dispersal  are  so  slight 
that  it  tends  to  concentrate  upon  any  tree  infested  until  the  latter 
becomes  completely  covered  by  it,  a  fact  which,  taken  together  with 
its  numerous  generations,  its  rapid  rate  of  multiplication,  and  its 
freedom  from  parasites  capable  of  overcoming  it,  make  it  the  dan- 
gerous enemy  which  it  has  become. 

The  San  Jose  scale  can  be  destroyed  by  the  winter  use  of  one  of 
the  lime  and  sulphur  mixtures,  which  may  either  be  purchased  ready- 
made  in  condition  for  use  by  dilution  only,  or  may  be  brought  into 
solution  by  boiling  the  raw  materials  together  according  to  the  fol- 
lowing directions. 

Materials :  15  pounds  of  lime,  15  pounds  of  sulphur,  and  50  gallons  of 
fairly  soft  water.  For  50  gallons  of  the  spray,  heat  12  gallons  of  water  in  a 
4O-gallon  iron  kettle,  mixing,  in  the  meantime,  in  a  separate  vessel,  15  pounds 
of  sulphur  with  enough  water  to  form  a  thin  paste.  Add  this  sulphur  to  the 
water  in  the  kettle  and  bring  the  mixture  to  a  temperature  just  below  boiling. 
Then  add  15  pounds  of  best  lump  lime,  keeping  cold  water  at  hand  to  use  as 
the  mixture  threatens  to  boil  over.  After  the  lime  is  fully  slaked,  boil  for 
40  minutes,  with  almost  constant  stirring.  Then  strain  into  a  5O-gallon  spray- 
tank  and  fill  with  water,  which  had  better  be  warm,  although  cold  water  will 
do.  To  prepare  100  gallons  of  the  spray  at  a  time,  heat  20  gallons  of  water 
in  the  40-gallon  kettle,  add  30  pounds  of  sulphur — previously  reduced  to  a  thin 
paste  with  water — and  to  this  put  30  pounds  of  lime.  Boil  as  before,  and 
dilute  to  100  gallons. 

If  a  supply  of  steam  is  available  for  cooking  the  mixture,  this  will  be 
found  a  much  more  convenient  source  of  heat.  The  cooking  is  then  done  in 
barrels  or  other  vessels,  from  which  the  fluid  is  strained  into  the  spray-tank. 
The  disturbance  caused  by  the  introduction  of  steam  makes  stirring  unneces- 
sary. When  cooked  with  steam  the  mixture  does  not  ordinarily  become  so 
dark  as  when  boiled  over  a  fire,  but  the  insecticide  effect  is  nevertheless  the 


IMPORTANT    INSECTS   OF   ILLINOIS    SHADE   TREES   AND    SHRUBS  523 

PUTNAM'S  SCALE 
(Aspidiotus -ancylus  Putnam) 

This  is  a  circular  or  oval,  dark  gray  or  black,  scale  insect,  about 
one-twelfth  of  an  inch  in  diameter,  with  a  brick-red  point  at  one  side 
of  the  center.  It  closely  resembles  the  San  Jose  scale  in  general 
appearance,  but  does  not  present  the  conspicuous  ring  and  nipple 
structure  of  the  latter,  altho  the  young  have  usually  a  nipple  and 
a  rather  indefinite  ring. 

It  passes  the  winter  but  partly  grown,  but  differs  from  the  San 
Jose  scale  in  the  fact  that  it  reproduces  by  means  of  eggs  laid  in 
late  spring  or  early  summer.  There  is  but  one  generation  in  a 
season. 

It  has  been  found  on  elm,  willow,  oak,  hemlock,  mountain  ash, 
Ilex,  white  birch,  Primus,  ash,  beech,  hackberry,  linden,  maple, 
Osage  orange,  and  water-locust.  It  is  rarely  injurious  enough  to 
require  special  attention. 

THE  WALNUT  OR  WILLOW  SCALE 
(Aspidiotus  juglans-regice  Comst.) 

This  species,  altho  common  on  a  number  of  shrubs  and  shade 
trees,  is  of  little  importance  except  on  the  willow,  to  which  it  is  a 
veritable  pest.  It  is  easily  distinguished  from  other  scales  of  the  San 
Jose  relationship  by  its  relatively  large  size,  its  diameter  being  3 
mm.,  or  an  eighth  of  an  inch.  The  female  scale  (Fig.  63,  a,  e,}  is 


Fig.  63.    Walnut  Scale,  Asp'diotusjuglans-regia:   a,  b  female  and  male  scales, 
enlarged;  c,  male  pupa;  d,  e,  male  and  female  scales,  natural  size. 

circular,  flat,  with  a  prominent  pink  or  reddish  point  at  one  side 
of  the  center.  The  male  scale  (Fig.  63,  b,  d)  is  elongated,  with  a 
corresponding  point  near  one  end.  The  female  passes  the  winter 
as  an  adult,  and  lays  her  eggs  in  early  spring. 

Treatment  the  same  as  that  for  the  scurfy  scale. 


524  BULLETIN  No.  151  [October, 

THE  COTTONY  MAPLE  SCALE 
(Pulznnaria  vitis  Linn.) 

The  cottony  maple  scale  (Fig.  64)  is  one  of  the  best  known 
scale  insects  because  it  heavily  infests  several  very  common  shade 
trees,  and  because  the  cottony  masses  beneath  the  body  of  the  adult 
female  in  early  summer  make  it  a  very  conspicuous  object.  These 
large  white  masses  are  a  deposit  of  waxy  threads  within  which  are 
the  minute,  oval,  pale  yellowish  eggs. 

The  history  of  this  insect  in  Illinois  since  1867  exhibits  suc- 
cessive periods  of  abundance  and  of  scarcity,  each  averaging  about 
four  or  five  years  for  the  state  as  a  whole.  That  is,  thruout 
some  considerable  part  of  the  state,  and  often  over  most  of  it, 
the  maple  scale  has  been  injuriously  abundant  once  in  eight  or  ten 
years,  and  its  period  of  abundance  has  lasted,  as  a  rule,  about  half 
this  time.  In  any  given  locality,  however,  it  has  usually  been  in- 
jurious for  a  much  shorter  time,  often  for  not  more  than  one  or  two 
years.  The  cessation  of  its  injuries  and  its  virtual  disappearance 
from  the  trees  infested  by  it  have  seemingly  been  due  almost  wholly 
to  the  agency  of  its  insect  enemies. 

The  soft  maple  (Acer  saccharinum)  is  the  tree  most  generally 
and  heavily  infested  by  this  insect.  The  hard  maples,  on  the  other 
hand,  are  infested  but  slightly  if  at  all.  The  box-elder  is  also  greatly 
subject  to  injury,  and  next  to  this,  perhaps,  the  linden  or  basswood. 
Among  the  other  trees  and  woody  plants  often  more  or  less  injured, 
are  the  elm,  honey-locust,  black  locust,  black  walnut,  sumac,  willow, 
poplar,  beech,  hawthorn,  bittersweet,  grape-vine,  and  Virginia  creep- 
er. We  have  found  mature  egg-laying  females  on  the  horse-chest- 
nut, honeysuckle,  dogwood,  trumpet-creeper,  mulberry,  snowberry, 
smoke-tree,  Spiraa,  false  syringa  (Philadelphus},  and  Wistaria. 
Oak,  ash,  and  catalpa  are  not  infested  in  northern  Illinois,  but  injury 
to  oaks  is  reported  from  Georgia.  The  pear  is  said  to  be  most  liable 
to  injury  among  the  fruit  trees,  and  apple,  plum,  and  peach  are 
sometimes  infested.  Serious  damage  to  fruit  trees  is,  however,  very 
unlikely.  The  migrating  young,  which  are  often  washed  from  trees 
by  rain,  or  blown  off  in  considerable  numbers,  may  maintain  them- 
selves for  a  time  on  a  great  variety  of  woody  and  herbaceous  plants, 
those  on  the  latter,  of  course,  perishing  with  the  advent  of  frosts. 

In  early  summer  this  scale,  when  very  abundant,  coats  the  under 
side  of  heavily  infested  limbs  with  a  thick  layer  of  cotton-like  waxy 
masses,  each  projecting  from  beneath  a  brown  cap  or  scale — the 
flat  body  of  the  mature  female.  This  "cotton"  is  secreted  and  the 
eggs  are  deposited  within  it  in  late  May  or  early  June  in  the  latitude 
of  central  Illinois,  but  usually  one  or  two  weeks  later  in  the  Chicago 
district. 

Something  over  3,000  eggs  are  usually  laid  by  each  female,  the 
number  ranging,  in  our  counts,  from  2,856  to  3,863,  with  an  average 


IMPORTANT  INSECTS  OF  ILLINOIS  SHADE  TREES  AND  SHRUBS  525 


Fig.  64.    A  Soft  maple  twig  badly  infested  with  adults  of  the  Cottony  Maple  Scale, 
Puivinaria  vitis.    About  natural  size. 


526 


BULLETIN    No.    151 


[October, 


of  3,410.  In  central  Illinois  the  eggs  ordinarily  hatch  in  June,  and 
in  the  northeastern  part  of  the  state  in  early  July,  of  later  if  the 
weather  of  the  time  is  unfavorable.  Virtually  all  are  hatched,  as 
a  rule,  by  the  end  of  July. 

When  first  hatched  the  six-legged  young  (Fig.  65,  a,  e,  /)  move 
slowly  about  as  creeping  yellowish  specks  about  twice  as  long  as 
wide.  They  soon  settle  upon  the  leaves,  mostly  upon  the  under  side 


Fig.  65.  Cottony  Maple  Scale,  Pulvinaria  vitis,  immature  stages:  a,  newly 
hatched  young,  under  side;  b.  c.  young  female,  top  and  side  views;  d, 
young  mdle;  «,/,  young  on  leaf  and  leat  stem.  Natural  size  shown  in  a. 

along  the  veins,  but  a  considerable  percentage  also  on  the  upper 
surface.  Soon  after  settling  down,  a  thin  waxy  layer  forms  on  the 
back,  and  in  about  three  weeks  the  insect  has  virtually  doubled  in 
size.  As  they  increase  in  size  the  male  and  female  scales  become 
distinguishable  (Fig.  65,  b,  c,  d)  by  the  fact  that  the  former  are 
comparatively  narrow  and  more  convex.  From  these  the  winged 
males  (Fig.  66,  a,  b,  c}  emerge  to  fertilize  the  stationary  females 
in  August  and  September,  perishing  soon  thereafter.  In  autumn 
the  young  females  migrate  from  the  leaves,  which  are  about  to  fall, 
to  the  twigs,  upon  wrhich  they  pass  the  winter  and,  indeed,  the  re- 
mainder of  their  lives.  In  spring  the  female  scale  (Fig.  67)  is  ellip- 
tical, convex  on  the  back,  with  a  low,  rounded,  median  ridge.  It  is 
pale  greenish  or  whitish  yellow,  marked  with  black  or  dark  brown. 
When  full  grown,  about  the  middle  of  May,  it  is  4  to  6  mm.  long 
and  3  to  4.5  mm.  wide.  Its  body  is  at  first  closely  applied  to  the  sur- 
face of  the  twig,  but  with  the  development  of  the  eggs  beneath  it  the 
abdomen  is  gradually  raised  from  the  bark  to  an  angle  of  forty-five 
degrees  or  more. 

It  is  usually  difficult  to  say  whether  trees  infested  by  this  insect 
should  receive  special  treatment,  or  whether  they  may  be  safely  left 


IMPORTANT  INSECTS  OF  ILLINOIS  SHADE  TREES  AND  SHRUBS 


527 


to  the  natural  course  of  events.  The  cottony  maple  scale  is  ex- 
tremely subject  to  parasites  and  attacks  of  other  insect  enemies, 
particularly  to  the  black  hemispherical  ladybugs  and  their  larvae,  the 
latter  of  which  feed  upon  the  egg  masses  in  spring  and  summer. 
With  an  extraordinary  abundance  of  the  scale  insects  themselves 


Fig.  66.  Male  of  Cottony  Maple  Scale,  Pulvinaria  vitis:  a,  adult; 
b,  c.  antenna  and  leg  enlarged;  d,  e,  second  stage  of  pupa  and  its 
cast  skin;  /,  g,  true  pupa  and  its  cast  skin.  All  greatly  enlarged. 

these  insect  enemies  improve  the  opportunity  for  unusual  multiplica- 
tion in  a  way  to  produce  a  greater  number  than  can  possibly  be 
maintained  permanently  by  the  scale  insects.  A  check  is  thus  put 
upon  the  increase  of  the  latter  which,  within  a  few  months,  may  re- 
duce them  to  insignificance.  The  consequence  is  an  irregular  peri- 


Fig.  67.  Cottony  Maple  Scale,  Pulvinaria  vitis. 
Adult  female  in  spring,  just  before  the  forma- 
tion of  the  cottony  egg  sac.  Enlarged. 

odicity  in  the  numbers  of  the  cottony  maple  scale  such  that  two  years 
of  injurious  abundance  rarely  succeed  each  other  in  the  same  place. 
Nevertheless,  where  trees  are  evidently  suffering  from  the  scale  at- 
tack it  is  always  prudent,  and  often  necessary,  to  take  artificial 
measures  of  protection. 


528  BULLETIN    No.    151  [October, 

As  the  newly  hatched  young  are  especially  susceptible  to  the 
petroleum  insecticides,  which  act  by  contact,  a  definite  knowledge  of 
the  hatching  period  has  an  important  practical  value.  In  central 
Illinois  this  period  extends  approximately  from  June  15  to  July  20. 
In  and  about  Chicago  it  commonly  begins  about  two  weeks  later,  and 
continues  for  a  period  of  three  weeks,  this  retardation  being  appar- 
ently due  to  the  higher  latitude  and  to  the  neighborhood  of  Lake 
Michigan.  The  period  varies,  in  short,  as  to  its  beginning  time,  with 
the  advancement  of  the  season,  and  once  begun,  the  rapidity  of  the 
hatching  will  depend,  other  things  being  equal,  on  the  warmth  of  the 
weather.  It  is  also  influenced  locally  by  the  amount  of  foliage  on 
the  trees,  the  eggs  hatching  later  and  more  slowly  in  a  dense  tree- 
top  than  in  one  more  open  to  the  sun. 

The  only  insecticides  available  against  these  insects  are  those 
which  kill  by  contact,  and  of  these  the  kerosene  mixtures  have  thus 
far  been  found  the  most  useful.  Even  these  can  be  applied  only  to 
the  young  scales  shortly  after  they  hatch  from  the  egg,  no  insecti- 
cide treatment  being  available  for  the  destruction  of  the  large  and 
conspicuous  females  upon  the  twigs  in  May  and  June.  The  common 
kerosene  emulsion,  made  by  thoroly  and  intimately  mixing  kero- 
sene with  one-third  of  its  volume  of  a  strong  soapsuds,  is  a  satis- 
factory spray  when  diluted  to  contain  ten  percent  of  kerosene  for 
summer  use,  and  sixteen  to  eighteen  percent  is  used  in  winter.  As 
a  summer  spray  this  emulsion  must  be  used  twice  in  succession,  once 
when  about  half  the  eggs  are  hatched  and  again  about  ten  days  there- 
after. A  single  treatment  in  winter  is  about  the  equivalent  in  prac- 
tical effect  of  two  such  summer  sprays.  Large  trees  in  a  sandy  soil, 
and  especially  those  in  more  or  less  unthrifty  condition,  should  be 
guarded  against  possible  injury  to  the  roots  from  the  dripping  of  the 
kerosene  spray,  or  from  that  part  of  it  which  may  run  down  the 
trunk  and  so  reach  the  earth.  For  this  purpose  it  would  be  well  to 
cover  the  ground  before  spraying  with  a  thin  layer  of  straw,  packed 
closely  around  the  base  of  the  trunk,  and  later  to  gather  this  up  and 
carry  it  away. 

The  cost  of  materials  for  large  trees  will  average  approximately 
fifteen  cents  a  gallon  for  the  summer  spray,  and  about  twice  as  much 
for  the  winter  strength. 

Kerosene  emulsion  is  made  as  follows :  Dissolve  one  pound 
of  common  soap,  or  half  a  pound  of  whale-oil  soap,  in  one  gallon  of 
water  by  boiling,  remove  from  the  fire,  and  add  two  gallons  of  kero- 
sene. Then  with  a  spray  pump  force  the  mixture  back  into  itself  for 
about  five  minutes,  or  until  it  presents  the  appearance  of  a  thick 
cream  and  no  longer  separates  on  standing.  This  is  the  undiluted 
emulsion.  For  a  mixture  containing  ten  percent  of  kerosene,  add 
seventeen  gallons  of  water  to  the  three  gallons  thus  prepared.  For 


IMPORTANT  INSECTS  OF  ILLINOIS  SHADE  TREES  AND  SHRUBS 


529 


an  eighteen-percent  kerosene  emulsion,  add  eight  gallons  of  water 
to  the  stock  emulsion.     Soft  water  is  to  be  preferred. 

The  following  tables  will  show  the  effects  of  kerosene  sprays 
as  applied  by  us  in  1905  and  1906. 


SUMMER  SPRAY 


Treatment 

Insecticide 

Part  of 
hatching 
period 

No.  of 
trees 

Leaves 
ex- 
amined 

Scales 
ex- 
amined 

Percent 
killed 
by  spray 

10  percent  kerosene  

Beginning1 

i 

48  78^ 

10  percent  kerosene   .      ... 

Middle 

1 

50 

19,425 

64 

10  percent  kerosene  

End 

3 

150 

281,271 

68 

10  percent  kerosene  

Middle 
and  end 

1 

100 

57,179 

82 

WINTER  SPRAY 


When  sprayed 

Percent 
of 
kerosene 

Date  of 

counting 

Scales 
counted 

Percent 
killed 

December  26  to  January  5 
(once)  

19 

Feb.  1 

12,703 

86 

January  11  to  13  (once)  

20 

Feb.  1-2 

23,061 

91 

January  11  to  13  and  March  30 
(twice)    

19-24 

June  10 

48,395 

91 

m 


UNIVERSITY  OF  ILLINOIS-URBANA 

711  CD 


